You have to learn the basics, and find projects or come up with your own projects, and go for it. It’s best to take some classes to learn the basics of how to structure your code, and the concepts of programming (like object oriented programming, model view controller structure, ect.). But My understanding is your on the younger side, so classes may not be an option (at least, they weren’t for me when I was younger). So your best option is online guides and coding forums for help when your confused or don’t know what you should do.
GL and let me know if you ever need any help.