Check for local clubs, and see if any offer rides for 'new riders'. You'll probably have to have your parents show up to the first ride, just to sign a release form and verify that they grant permission for you to ride. The ride leader will usually go over some basic skills (braking, turning, shifting) in a parking area, and then take you all out for a short ride on the roads with an experienced sweep rider who will observe your group riding skills (or lack thereof) and offer suggestions that will make you a safer rider, and welcomed on regular club rides.