I know the principles of that style of training, yes... but you'd be much better off asking on the bodybuilding.com forums from people who have a background in that sort of training

What I will say that it's about training explosively and eating a lot of clean calories and giving muscles time to heal, you'll gain some fat but you can't gain much muscle mass unless you are eating more calories than the ones your body is using.

You burn the fat off later.

At 15 I don't know how much your going to put on, your body is more bothered about growing your bones, brain, heart, blood vessels and lungs at that age than growing a lot of muscle tissue.

In a few years you will find it hard not to gain weight...

I can't really be any more specific, As I say I know the principles of it all but my training background is purely in conditioning, and not the type of strength conditioning which is going to give huge size gains at that.

There are some good forums out there with people who know about Cosmetic/Aesthetic training and have experience in it.

namely http://forum.bodybuilding.com/ and http://forums.overclockers.co.uk/forumdisplay.php?f=13