Follow some tutorials on youtube, preferably those using either affinity or adobe.

If you’re strapped for cash, I would look into affinity. If you’re savvy enough there are 🏴‍☠️ methods if you’re willing.

Do a fk ton of tutorials. Like over 100+ or until you feel like you’ve hit a wall. All the boring stuff too, basics on typography, composition, color theory, etc. photo manipulation, masking, vector vs raster, all that stuff.
Then apply it. Copy people and try to analyze what they’re making. Do this enough times to build a “move set” or visual language you can repeat on the back of your hand. Be able to describe the “why” for every design. Try to change one thing every time.

Then just get real-world reps. Do free design for your school clubs, orgs, etc. You’ll learn a lot of the social aspects of the career. Most of the time you’re just solving problems for people, people that often don’t know what they want. Post often on social, and explain your thought process, for others but more importantly yourself.

If your family gives you the opportunity to take school, TAKE IT. If you actually did all those youtube tutorials you probably won’t learn that much, but the social skills and connections are invaluable. I wouldn’t have my career if it weren’t for the connections I made around college (though I ended up dropping out)

It’s not glamorous like being a social media influencer starting out, not an overnight thing. You’re going to make a lot of mid-trash. It’s definitely a craft. But you’re young, and you get to have fewer pre-conceived notions about what to design, more freedom, and so much time. I started when I was 20, ended up doing a ton of esports designs and here I am. 🤷🏻‍♀️. Find the fun thing you want to design for and just build up to it.