How do I gain muscle weight?

Hi. I'm a 14 year old boy who wants to gain muscle. I know a lot of people are going to say I'm underage but I do only body weight exercises and that doesn't stunt growth. Okay my question is, how do I gain muscle weight. I do the workouts but what should I do about the nutrition? Do i eat more calories than i burn? Will the extra calories turn into fat or muscle? What is the process and how do I do this? Thanks!