How to lose weight for a 13 year old boy?

Im 13 and im 121 lbs and Im 5.5 1/2. Im average but how can I lose weight and be really skinny. People say I have chubby cheeks and I want to get rid of them. I’ve look around and have found that losing weight helps. So, in my case, how can I lose weight and maybe form a well built body(4 pac or 6 pac or w.e).