First welcome to the insanity of classic Airstream ownership.
Your front air bags want to be 55 psi. that should soften the ride a bit. Next the rear bag operation should be automatic. The compressor located in the left rear storage compartment, should start when the ignition switch is turned on. The air pressure is controlled by an automatic pressure switch that turns the compressor at about 70 psi. and off at about 100 psi. The air bag pressure is controlled by a leveling valve that adjusts the bag pressure to keep the rear of the coach at a specific ride height. If you look under the rear of the coach the height of the bags, the distance between the cross member at the bottom of the bags to the cross member at the top of the bags is supposed to be around 8 1/2" to 8 3/4". You will see a small rod about 1/4" dia. attached to the lower cross member and the leveling valve mounted on the upper cross member. Adjusting the arm on the leveling valve adjusts the ride height.
This is a picture of the system however it doesn't show the leveling valve.