Can someone please explain how to make homebrew? It is confusing.

That's a BIG ask. There is too much to explain and you’ve provided no specifics on where to start. I can point you to the basics, give you my top tips, and then answer some specific questions however. 

I hope this is helpful. 

 My Top Tips

Here are my personal top tips, others people will have other top tips. 

1. DON'T PUBLISH! (You will, but I'm trying to save you the headache I gave myself by publishing too soon.) As long as you don't publish it, you can fix it. (*Well... you can fix it if you publish it, but it's a pain in the neck, and it leaves ghost for you on the back end that make future mistakes more likely. As long as you don't publish it, you save yourself that headache.) I guarantee you 1 thing, you're eventually going to think you've got it nailed. You're gonna think that there is nothing left to improve. You're gonna say "To heck with it, I'ma publish it" and you'll hit that button. And a little while later, you'll find another new thing you didn't know existed before, or learn about another new thing you didn't know it could do before, you think "Darn it." (Wanna guess how I learned this one? That's right, the hard way.)
2. Ask. Ask right in this forum like you did. People will help you.
3. Read. Read all the questions you can that other people ask. You may not need to know that at the time, but if you Homebrew enough stuff sooner or later you will. 
4. Get feedback. Even if it's not published, you can copy/paste into these forums. Nobody will be able to use it, but they can read and give feedback. Even if it's not published your friends in campaigns with you can use them. Find out their thoughts.
5. Playtest. Nothing really “works right” until it has actually worked in-game. 
6. Publish. Because. That's the best reason. (I gotta tell you though, the longer you wait before this one, the less you will need the next one.)
7. Be prepared to want to go back and fix it. Because sooner or later, you will want to. 

 The Basics

A convenient article written by the DDB staff:

https://www.dndbeyond.com/posts/845-new-players-guide-how-to-homebrew-on-d-d-beyond

After that, probably the 1st & 2nd places to start
are here: *https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/3625-everything-you-need-to-know-about-homebrew. *(One thing to note, the title fibs. It is nowhere remotely “everything,” because that would be too much, that's how big an ask that is. But, it is “The Basics on how to Start Homebrewing Most Things on DDB” Basic 101 for Race/Subrace/Variant Races, Subclasses, Magic Items, and Spells). 
and here: https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/9536-d-d-beyond-video-tutorials-homebrew-feats, (“The Basics on how to Homebrew this Other Thing on DDB” (Basic 101 for Feats)

 You now when you look at the builder and it has a ton of fields with names that don’t seem to mean what you think they mean? And then there are more fields with names that don't seem to mean anything at all? And by the time you're halfway through you're not even sure about things like "Name" or "Description" anymore...?
Well... these cover enough about those to get you confident to try, but not enough to prevent you from messing up. That's okay, mess up, it's not a huge deal as long as you remember 1 thing: DON'T PUBLISH!

 The 3rd and 4th most practical official places to start are
and here: https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/25930-using-snippet-codes-in-your-homebrew (Snippets 101)
and here: https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/9811-how-to-add-tooltips. (Tooltips 101)

One of those fields with names that don't seem to mean anything is called "snippets." This 3rd link explains those. Those are the codes that get your character sheet to do calculations in the text that are based on numbers that change depending on your choices.

Tooltips are the codes that let you turn Fireball into Fireball.

Personally I would put these two lower down on the list, but those four links all come from actual DDB Staff. They are the official "How To"s, so I put these two with the other two. They are useful, and not actually complicated, but IMHO also not worth worrying about until you get comfortable the next part.

 5th & 6th: Truthfully, after you look over those first two links, the most useful place to start is actually a pair of places that taught me the most by using them together. This combination of tools taught me a ton, and I can learn at my own pace which is great. Just rinse and repeat as needed. 

• Up at the top of your screen tap/click "Game Rules" and then search through the official content. When you find a thing that does something you want to learn how to do, note what kind of thing it is (Feat, Magic Item, etc.) and what the name is, and then go to:
• Up at the top of your screen tap/click "Collections" then "Brows and Create Homebrew." When you click on the right kind of thing, it will ask if you want to use a template say yes and put in that name. 

 7th: Other people's homebrew. I only put this one as low as I did for two reasons: 1) There is a lot of it. For me, too much all at once in the beginning. 2) You can't crack it open to see how it works. Homebrewers are way more creative than the official content. So stuff gets combined in interesting ways, but you might not be able to puzzle it out if you don't already have some ideas about how it works. So the first 6 "basics" can help you figure these out better.

 *Editing after Publication

 The only way to edit after publication is to hit “create new version.” After that Look in your “creations” there should be two versions of it, the old one that you published, and the non-published copy. Once you edit it and republish, the new version will replace the old version for everyone else’s access, but you will have to manually remove the old version from your own “collection” or you will always see both versions. In future, don’t “publish” anything until it’s 100% done to save yourself the hassle. 

That button creates a new, unpublished version that got added to your “collection.” You have to navigate to that page where you should find two versions of your creation, one published, one unpublished. Expand the unpublished one and you can then hit “edit” which will redirect you to the editor. 

Every time you “create new version” it will do exactly that. So when you have two versions in your “creations” your characters (and the characters of everyone else in every campaign you are in) will also be able to choose either version. Unless you change the name, nobody will be able to tell one from the other until after that choose it. To avoid that, expand any versions that you are not happy with and hit “remove from collection” and then nobody can choose the wrong one. 

If you are still changing stuff, any version you are working on must be in your “collection” for you to test (add to a testing character or testing campaign) to see if it works. 

After you publish the new version, you still need to police your “collection” because it will not remove/replace the old versions. Others will no longer be able to access to old version (unless they are a subscriber and have added it to their own “collection”) but you will still get access to the old versions as  duplicates if you do not remove them. 

Even after that, those old versions will still haunt you in strange ways. For example, if you republish the same spell twice, even if you remove the two old versions from your collection. If you later make a homebrew Magic Item to cast that spell (like a wand or sword with charges) when you go to attach that spell to that item, you will still see all three versions, with no indication of which is the right one. And if it was the wrong version, and that version is no longer in your “collection” then it will attach correctly but that magic item will not work.

You do not need to publish anything. You and the others in every campaign you join will be able to use any unpublished homebrews in your “collection” anyway. Only publish if you are absolutely sure you never need to edit it again ever for any reason. 

Once published though, there is no way to delete a creation.

Thanks! It is mainly all the different fields that confuse me. How can I manage those?

Quote from Hellbringer_Player >>

Thanks! It is mainly all the different fields that confuse me. How can I manage those?

1.  Basics: 1st & 2nd and 5th & 6th
2. Top Tips: #2 and #3

I just want you to know that I wasn’t being dismissive. The reasons there are no quick answers to your question are,

• I don’t know which fields you need help with,
• and I don’t know what you’re trying to make. 

There are too many fields to explain them all without it being just as confusing as it is now. 

Not all of the fields work (or work the same ways) depending on what you’re trying to make.

If you tell me what you’re making (Spell, Magic Item, Feat, Subclass, Race/Subrace/Variant Race), and what and what you want it to do then I can be more helpful. 

OK, thanks! I have figured out a couple, by staying up until 3 AM.

Quote from Hellbringer_Player >>

OK, thanks! I have figured out a couple, by staying up until 3 AM.

 Happy to help.

I did that... a lot.... 😂 

Those resources I pointed you towards will help too. And, like I said, if you provide a little info others can help with most of the rest.

OK. I was trying to make a variant of the Eldritch Knight.

Okay, that helps. And what is it you want to change that doesn’t make sense?

I got it now. Never mind.

Okay, glad it worked out. 

Thanks!