Start the engine, and with the car up on axle-stands at the front end (your tyres will thank you for this, so will the rack and the pump!) smoothly turn the rack to full left and then full right a few times, with the lid removed from the power-steering fluid reservoir. DON'T LOITER at full lock, EVER, in a car with power-steering, it's very bad for it. As soon as you reach lock, ease back the other way. Do this a few times. Switch off, leave the car for around an hour if you can, repeat, and then fasten the lid on the reservoir. Road test with care at walking speed, do a few parking moves to ensure it's all good.

Turning the wheel lock to lock is no longer the recommended method and can damage the pump. The current recommendation is to use a hand vacuum pump and an adapter cap and pull a vacuum on the entire PS system.

Fill he reservoir to the correct mark, start your engine. turn the wheel all the way to the left, then all the way to the right. Just till you feel it bump. do this a few times. This should get the air out of the system. Then check your fluid again.

jack up the front and turn the steering wheel left and right with the engine off

Hither fact is has air present suggests something needs to be replaced so consult with a dealer of your make of car.