I feel you!! there's so much to learn it's hard to find a place to start. But I feel like there's no wrong place to start, as long as you keep going!
Echoing what the others are saying, learning up on music theory will make things a lot easier! I'd recommend starting by learning the basics of scales, intervals and chords. It is possible to create music without getting into theory, but theory does make it a lot easier to find patterns and put together your own original ideas, rather than just working within the limitations of your existing knowledge. I personally really enjoy theory but I might be in the minority there ;p
I found it really overwhelming to start with too but I promise once you get to a certain point it all starts making sense!!
Another thing I really recommend is ~active listening~. Find a song you like, and listen to it really closely, paying attention to every note. Try transcribing it, and/or playing it yourself. This is hard to begin with, but the more your do it, the easier it gets (and knowing theory makes it a million times easier). I find this seriously valuable; not only does it help you improve your ear, but it'll broaden your repertoire and also hopefully be inspiring. This is actually where I started out and I think it's a decent place to start. Again, theory isn't a prerequisite for this, but i'd highly highly recommend it.
Also I would highly recommend learning an instrument (if you're not already doing that) if you wanna get into composing. It can be any instrument as long as you're interested enough to pursue it! It's just REALLY helpful to be able to feel+hear what you're learning. Plus, it's a lot easier to mess around ideas with a physical instrument than it is slowly inputting notes into a score or pinao roll on your computer.
This point isn't a specific one on places to start but I still think it's really worth mentioning: speaking of inspiration, it's important to find stuff that inspires you and keeps you interested in learning. Getting into music is a bit like taking up drawing, in that it's a big case of delayed gratification-- nobody is good at it when they first start, and it takes a lot of time and effort to get good. So keeping yourself interested in practicing is super important! Find some music-related youtube channels and stuff like that which you enjoy. It'd put my faves here but they might not be the kinda thing you'd be into & I wouldn't wanna put you off :o also if you can find other musicians to jam with and/or share your stuff with that's really valuable too!
If you got any specific questions u can PM me if u like! not that I am a master or anything but I know some basics and would be happy to help👍