1991 chevy cavalier. how do i re-apply the caliber to the rotor?

Jsdurand88, It sounds to me like you just replaced the brake pads although it is not mentioned here. If this is the case then what you have to do is to push the caliper piston back into the caliper. A C-clamp will do just fine here. Use this to push the piston in until it stops and then you should be able to put the caliper back in place. When you put the caliper back be sure to lubricate the sliders. Be sure that you pump your brake pedal a few times before you actually drive the car. Pumping the pedal pushes the piston back out where it belongs for proper brake operation. Good luck with this.