Excercise help?

I am 12 and 95 pounds..i try to gain weight but it al goes to my stomach(runs in the family) so i went to seventeen.com and decided to to the broom stick crunchs..and like the energy thing to keep be in shape(not like very skinny to the point were u see ur ribs) but to just feel good, and get my muscles toned so is it a good idea for me?(and i know i am 12 but i want to look good and feel good)