Safely raise the car so both rear wheels are suspended.
With parking brake released turn a lug bolt hole until you can reach the star wheel with a screwdriver to loosen the parking brake shoe. It is slightly forward from the top.
Unbolt caliper and suspend it with wire, do not let it hang on the hose, or drop it causing a strain on the hose.
Pull rotor off.
Clean mounting surface with a steel brush.
Push rotor in place and reverse procedure.
Happy New Year,