Question about boxing?

I'm 13. I have wanted to box for as long as i can remember. I almost joined a boxing gym to start on the road to becoming an amateur boxer but my brother (former boxer) persuaded me to play football instead. Anyway, my mother said if i can get a "boxer's physique" then she will let me join a boxing gym, and get me trained. I'm part of a small gym that i have been going to sense school got out, the problem is i don't know what im doing. what do i need to do at the gym, or work on in the gym to get a "boxer's physique". if you could sketch out a weekly workout regimen that would be a very big help. also, any tips on what to eat? im eating a lot of protein and water right now. Thanks in advance :)