The most important thing is to start learning a programming language.
And the best way to do that is to start a real small project. Come up with a small idea that scratches an itch, then plan it out on paper and start executing stage by stage.
If you want to go ahead into college, you will then have an ENORMOUS leg up on everyone else and school will be a breeze.
If you wait until you go to school then it will be as hard as anyone else.