Go to the airport closest to where you live and find out. Tell them that you want to learn how to fly, talk to the instructors, ask them to take you for an introductory flight, find out about the cost, find out about everything you want to know...if you think you'll be happy there sign up for your first lesson. Have you flown before? Obviously you have never soloed because you are 15 years old at most but you may have flown with somebody who let you hold the controls in flight.
The other thing you can do is subscribe to a magazine like AOPA, Flying, or Private Pilot...one of those. If you read any of those, you'll find adds about good aviation schools. You should also look at Sporty's pilot catalog, you'll find a lot of good stuff in it including a wide variety of books. Go to a library and find out.