How do i enhance and what do i do to get buff body?

I am 15 years old boy,i m kinda skinny a lil hunchback.i m 167 tall,40kg weight.I need advise on what is should it and do to get overcome hunchback problem and my skinny-type body.Your answers would be very helpful so that i won't be hesitate to go to a swimming pool or take off my shirt in public.And pleas recommend on what should i take for my daily nutrition.