how do you bleed the air from a power steering pump

Just start the car and turn the steering wheel from lock to lock about 20 times and it will bleed itself. It helps to have the front wheels off the ground. If your pump is still weak after doing that its either defective, hooked up wrong, or there could be a problem in the steering box.

Make sure the vehicle is off, otherwise you will cause the air in the system to cavitate causing air bubbles to spread throughout. Jack up the front end, remove the power steering reservoir cap and slowly turn the steering wheel from lock to lock, ensuring the reservoir has fluid in it. That will properly bleed the system.