im a new player and dm to DND in general and I have no idea how to make a subclass for homebrew,I basically made a martial sorcerer subclass that casts using con instead of charisma and is much more melee focused,but I'm too busy and kinda dumb to make it a reality can someone help me?please

If you're new to D&D, don't try and make homebrew. Instead play the game a bit, learn how the game works, build a knowledge base of how the elements of the game interact. Then circle back and start trying to homebrew. For example, you wouldn't try and make your own cake recipe without any foundational of knowledge in baking.

For your concept, maybe just play an eldritch knight or warlock and reflavour it to suit your idea.

If you are a new to DnD and a therefore new to DM, you might want to also find some premade adventures, to better understand how the game works.  Even experienced players can find being a new DM a very different experience that involves different types of knowledge and different prep (quantity & type).

Quote from light_gaming >>

im a new player and dm to DND in general and I have no idea how to make a subclass for homebrew,I basically made a martial sorcerer subclass that casts using con instead of charisma and is much more melee focused,but I'm too busy and kinda dumb to make it a reality can someone help me?please

The simplest way is just have a DM fiat that you use your con instead of cha.  Nothing else to change.

There's a reason that CON isn't a stat used as a spellcasting ability. CON already grants bonuses elsewhere. What you're trying to do here is create a god-tier character build that will not only have super-duper HP but also have high spellcasting bonuses. The reason CHA, INT, or WIS are the spellcasting abilities is basically to not allow double-dipping on bonuses and make choosing which ability scores to improve be a meaningful choice. 

Effectively to do what you're suggesting removes meaningful player choice from the character build. 

If that's what you want to do, I'd simply take a standard existing class and say that their casting ability is switched with CON.

I'd also strongly echo Davyd's comments though - learn the game first before you try to 'improve' it. It's the same with most things, once you learn the rules they are much easier to break without breaking the entire system.

There's a homebrew section in the forums that can answer this kinds of questions with the homebrew tools. I Haven't played with spellcasting feature to tell you how to change the casting stat, but it is something editable somewhere. Since is for your own game, have at it.

As for the recomendations to play a little more of the "base" game until you have a handle of the rules, its solid advice and will help you with balancing other aspects of your game.

Quote from martintheactor >>

There's a reason that CON isn't a stat used as a spellcasting ability. CON already grants bonuses elsewhere. What you're trying to do here is create a god-tier character build that will not only have super-duper HP but also have high spellcasting bonuses. The reason CHA, INT, or WIS are the spellcasting abilities is basically to not allow double-dipping on bonuses and make choosing which ability scores to improve be a meaningful choice. 

Effectively to do what you're suggesting removes meaningful player choice from the character build. 

If that's what you want to do, I'd simply take a standard existing class and say that their casting ability is switched with CON.

 

I'd also strongly echo Davyd's comments though - learn the game first before you try to 'improve' it. It's the same with most things, once you learn the rules they are much easier to break without breaking the entire system.

 Wait. Do you have access to the Eberron books? Or the Elemental Evil Player's Companion? Because the first provides a feat where Con is a spellcasting ability and I think the second provided a race that did the same...

But as for learning the game first... I do agree.

yeah I gave up on that a little while ago lol and no I don't have access to anything past basic rules and free claimables

Quote from light_gaming >>

yeah I gave up on that a little while ago lol and no I don't have access to anything past basic rules and free claimables

 Oh.

The main thing is I think to determine spellcasting ability you have to make a class, unless the original class didn't have a spellcasting ability (just advice for the future).

And I think you can get the Elemental Evil Player's Companion as a free PDF download somewhere, might want to look into that. I don't know if it's usable on DDB that way but you could add the races in it as private 'homebrew' in order to use them.

Quote from Golden_Axolotl_Dragon >>

 Wait. Do you have access to the Eberron books? Or the Elemental Evil Player's Companion? Because the first provides a feat where Con is a spellcasting ability and I think the second provided a race that did the same...

But as for learning the game first... I do agree.

 
I think you're talking here about Dragonmarks - Abberant Dragonmark allowed the casting of I think 2 spells using CON as a modifier. It didn't make Constitution your modifier for every spell. This effectively boiled down to a one-per-rest ability that was skinned as a spell.

As for the EEPC you're talking about Genasi here. Again, your spellcasting ability wasn't flatly changed to be CON, rather you gained a once per long rest ability that was fuelled by your CON, despite being written as a spell. 

In both cases these are exceptions to a rule not the rule in specific. It's worth highlighting too that when reprinting these races in Monsters of the Multiverse the accusations of power creep were clearly heard because the Genasi's abilities were retconned to be INT, WIS, or CHA. To me that kinda puts the nail in the coffin of why CON is a bad choice for a spellcasting ability. It would effectively wipe out any reason to choose any other race (species) or class.

Don't misunderstand, if a GM feels that this works for their table that's great and they should do it. For a newbie though there is a design reason within the game why CON isn't used to fuel spellcasting in most cases. A high CON score has SO many benefits that making it a spellcasting ability is just asking for players to only ever buff their CON score. 

Quote from martintheactor >>

I think you're talking here about Dragonmarks - Abberant Dragonmark allowed the casting of I think 2 spells using CON as a modifier. It didn't make Constitution your modifier for every spell. This effectively boiled down to a one-per-rest ability that was skinned as a spell.

As for the EEPC you're talking about Genasi here. Again, your spellcasting ability wasn't flatly changed to be CON, rather you gained a once per long rest ability that was fuelled by your CON, despite being written as a spell. 

In both cases these are exceptions to a rule not the rule in specific. It's worth highlighting too that when reprinting these races in Monsters of the Multiverse the accusations of power creep were clearly heard because the Genasi's abilities were retconned to be INT, WIS, or CHA. To me that kinda puts the nail in the coffin of why CON is a bad choice for a spellcasting ability. It would effectively wipe out any reason to choose any other race (species) or class.

Don't misunderstand, if a GM feels that this works for their table that's great and they should do it. For a newbie though there is a design reason within the game why CON isn't used to fuel spellcasting in most cases. A high CON score has SO many benefits that making it a spellcasting ability is just asking for players to only ever buff their CON score. 

I forgot to consider the fact that these were limited in scope. I do agree for the most part, I was just noting that using CON for spellcasting isn't something that is completely outside of what has been done before (although only for 1st level spells, admittedly).