Becoming a witch is a choice you make. It is rare that someone is inherently a witch; usually, they feel drawn towards witchcraft. You can start right where you are. I have lots of articles that will help you get started.
If you are young, and you think your family wouldn't approve, then you should hold off with the whole witchcraft thing. However, that doesn't prevent you from learning as much as you can until the time is right. If your family is easy-going, then you can just gently slide into being a witch by small actions: leave a witchy book lying around, ask for a tarot deck as a gift, wear slightly more witchy clothes (if that appeals). Practice visualizing getting a good parking space for whoever's driving, then joke about it and tell them it's witchcraft. Keep it light.