10mm deep socket with a 1/4inch rachet drive.
right where the ebrake handle is, you pop up the surrounding piece trim and there is a little nut and just tighten it.
if that doesnt work then it might mean you may be needing new brakes i believe.
im where you are at right now, my brakes tend to move even when its pulled to the very top, so i put bricks and stoppers behind the wheels to prevent it from moving. and i am needing new brakes.
hope that helped.