Noob to homebrew creations, here. 

I'm currently trying to create my own Paladin Oath based off a specific song. I also need to modify the Class, itself, by being able to add spells from the Warlock, Cleric, and Druid lists, while also maintaining the Paladin spell lists.

I'm not sure how to accomplish this with the Homebrew creator. I've dabbled in the subclass area, but I'm very easily getting confused. And I can't seem to find anything helpful within the threads.

Send help! I have a lot of work to do before this weekends session!

I'll be happy to share notes on what I'm creating for those that are curious and are fans of the general Rock genre of music.

You cannot alter the base Paladin class at all. You can still add the spalls though. Do you want them as the Always Prepared “Oath Spells,” or do you want them simply added to the list from which they could learn?

So a simple breakdown of it is that he's pulling "favors" from unnamed gods each day, whoever is willing to take pity on him. Sooooo, each day I randomly pick out his spells and either prepare them for him, or give him "the list of the day" to prepare from. It's completely random if he'll have full Pally spells and abilities, or a combination of Cleric/Warlock, or just strictly Cleric/Warlock. I'll be rolling dice to determine what is what.

I'm still playing around with what I'm going to finalize, but I'm just trying to figure out how I can add these spells and create a new oath for him to choose.

There are two ways you could do that:

Under “Basic Information” for the subclass, you could just add Warlock and Cleric to the “Additional Spell List” field. That would be easier for you to do since it’s, like, 4 clicks total and you’re done. The downside is that any spells that appear on more than one of those lists will appear multiple times in the list for the player.

You could make a class feature for the which explains everything just like any other class feature. At the bottom of that feature you will see a section labeled “Additional Spell List.” (I know that’s a little confusing, same name, works totally different.) Click “Add A Spell List” and then under the “Expanded Spells” field you could add each spell that you want added. It will take longer for you since they will all have to be added individually, but you could avoid those duplicates so it will look cleaner for the player, and they will have a little icon on the character sheet which will make them easier to spot too.

The first one sounds like it would work.

I decided, just now, that how I'm going to do it is make up my own spell lists. Basically, each day he'll wake up and his "talisman"/holy symbol will be radiating a different color. That color is determined by a roll of a dice(I have to do some math to figure out which die) and then he'll recieve a list of spells that he can choose from to prepare for the day. 

Basically, he'll just have access to all spells, but I'll only allow him to select from these certain spells.

I've been talking with him (he's hubby) on what makes sense to him and what he's comfortable with and so far this seems to be the easiest bet, for now. 

Adjusting the homebrew was my next hurdle. I'll try the first suggestion and if it doesn't work, I'll come crying back to you xD

No problemo.