Ok, the proper way is to squeeze the piston using a c clamp as shown in the picture. Without one, you can insert a screwdriver down through top of caliper and wedge betwwen a pad and the rotor and pull the driver so the piston goes in a little.
Thenn you go to the top bolt of the caliper #2 in the picture. You remove that bolt/pin and the caliper will swing down and you swap out the pads. the top bolt is uaully a TORX type bolt and the size is T55 on most. You cna get a TORX bit at any local parts store. If it looks like a star? its a TORX bolt, if allen? then its a 3/8th allen wrench to remove the bolt