What do I need to join an prep school?

Hello, I am in 8th grade and am applying to Groton, and I wanted to know what all I need to join Groton. I have a sibling studying in milton and I feel I (dont wanna brag) can keep up with the high academics and fast pace the studies go. I am afraid i lack sports and have not participated in any debate, speech,etc competitions yets nor have I taken any classes.