How do you adjust the rear ride height on air suspension

Usually you have two ride height valves on the rear axle and one on the front. It can be reversed but not often. Usually it's a simple rubber end attached to the axle and clamped to a metal rod that goes to an arm on the ride height valve mounted to the frame. Loosen the small hose clamp and pull the rod out 1" and re clamp on both sides.

You need to block the frame so you do not lower the rig on you if something goes wrong.