Only studio owners can remove other members.
Every studio has an "owner" who can manage the list of studio members. If you don't know who your studio's owner is, or to change the owner of a studio, contact email@example.com.
If you are the studio owner and need to remove another member, simply scroll down to the Members tab on the left-side navigation bar in your studio, and click an individual member's name. Then select the "Remove Members" button on the bottom right-hand side of the screen.