Good workouts to do at home?

i am 15 have time on my hands, i am 6' 2" and i am extremely skinny i am only 135 or 130 lbs so i want to gain weight and i wanna just gain muscle so i wanted a few ab workouts (even though since i am so skinny i already have a 6 pack) and some arm workouts because as of right now i can only do like 10 descent pushups in a row