Take painting classes, when you get to college, but also take drawing classes to sharpen up your skills. Take some history of art classes to get inspiration. Talk and make connections with people at your local art galleries.
This is a good question. . . You've received some great advice already and I'd like to share my experience for your consideration as well. I agree with Elena that some people are very talented from birth, and some need years and years of schooling. I have young nieces that are extremely talented in art from birth (ie, painting, making things (furniture), etc) but, they've chosen a different path as a career. The one thing I had to keep advising my nieces on was to make sure to "SIGN" your name and date the artwork because they would give paintings as gifts without their signature on it. Just make sure that you personalize your paintings with your signature mark, date, etc.
Best of luck to you!