Shut off the lawnmower.
Grab the handle that extends upward from the mower deck next to any wheel. Pull inward slightly to flex the handle away from the wheel.
Pull the handle toward the rear of the mower to raise the wheel to the desired height then release it so that the square cutout in the side of the handle locks onto one of the serrated prongs on the steel plate next to the wheel.
Repeat the adjustment with the remaining three wheels. Set each handle at the same height for level mowing.
Pull the handle inward then forward to lower the wheel height.