please help trying to recover11?

ok i am a 13 5’9 and 114 pounds, girl, and i need to gain weight because i recently lost a lot from being anorexic and now i need to be like 120 pounds. if i drink a protein shake what are some small like abb or thi workouts that i can just do in my room and that wont work my matabolism to much… workouts for muscle?also would it be bad to start running again now? when can i start to run because cross country starts in less than a month.
also before i lost i was 115 pounds