How to center the power steering?

I have a 70 Charger and a friend of mine has a 69 Coronet and both have a problem with the steering. Each will turn super hard to one side or the other and it's not a problem with the alignment. Even while the car is idleing and and in park it will just turn the wheel all the way. I have heard something about centering something on the power steering to fix it but I have no idea how to do that... Any ideas? thanks
Author: bvanetten1