Admins manage people under Admin → Members. Select "Invite" and enter email addresses to send invitations; pending invites can be resent or revoked. Each member can be assigned a role — Member, Admin, or Owner — which controls access to billing and security settings.
To free up a paid seat, remove a member or change their role; seats update on your next invoice. Removing a member doesn't delete meetings they hosted, but their cloud recordings may be reassigned to an admin.