Read, read, read. And I'm referring to articles from credible sites and of course, books. There are a lot of books out there designed in a lesson style for those starting out. I recommend these if you enjoy taking it slow and like a study session.
-Wicca: A Year and a Day by Timothy Roderick
-Wicca: The Complete Craft by D.J. Conway
-The Inner Temple of Witchcraft by Christopher Penczak (This is part of the Temple of Witchcraft Series that is very good)
-Dedicant: A Witch's Circle of Fire by Thuri Calafia
-Buckland's Complete Book of Witchcraft by Raymond Buckland
-Grimoire for the Apprentice Wizard by Oberon Zell-Ravenheart (designed for young adults - can be a bit fluffy, but I enjoyed it)
Scott Cunningham's books Wicca and Living Wicca are also good reads for beginners. I highly recommend them to get a basic understanding of what Wicca and magick really are.
The best way to get books is by explaining to your parents that you are just interested in learning about a different faith. Don't say you are wanting to switch but just learn about it so to better understand the world around you. Most parents will okay that. Maybe you can get your parents to take you to the public library and allow you to see what books are available there on Wicca, Paganism and Witchcraft. Many libraries have some good books you can check out and that way your parents can see exactly what it is you will be reading to ease their mind.
And another idea is to study online which I'm not as much a fan of. This is due to so many sites having information that is incorrect. However, a simple place to train is at www.witchschool.com as they have free lessons you an sign up for. One of them is a full year and a day course, that I took just to check out. It is very worth the effort.