REPAIR DETAILS

I was changing my brakes yesterday. Changed the front brakes completely fine but when I went to change the back brakes it seems my calipers are stuck. It seems I have a seized brake caliper. I tried to use a C clamp and push the caliper back in so I could put it back on and complete the brake installation but its completely stuck no matter how hard I tried. Looking for someone to help me fix this issue so I can complete my brake installation and then change the rear brakes on my other tire which I have not changed yet.