help!!!!!! Brakes are off I cant get the back on

I took off my brakes to my 2005 ford focus. Im at the part where you retract the piston so the caliper body will fit over the brakes I cant figure out how to move it back into place!!!! What do i do??????? I have been using a wrench to try to screw it clockwise. It will not budge. Someone please help.

On the front just push them back in with a C clamp. On the rear you might have to push with a C clamp and turn at the same time.