Unplug the refrigerator before doing any work on it. You can also turn off the power to the refrigerator at the circuit breaker, but it's better to unplug the fridge when you move it away from the wall.
Unscrew the screws holding the back panel covering the compressor, if necessary. Don't touch the compressor, as it may still hold an electric charge.
Find the overload protector on the back of the refrigerator. The overload protector is a box with wires going into it and coming out of it.
Remove the cover to the overload protector. It may or may not be held into place with a clip, which will have to be unscrewed. If there is no clip, you can gently pull the cover off.
Disconnect the overload protector from the refrigerator by pulling out the connectors with a pair of needle-nosed pliers. Pull the overload protector out of its housing.
Put a new overload protector into the housing. Reconnect the clip, if there is one. Put the connectors onto the wires coming out of the new protector. Put the cover back onto the overload protector and replace the back panel, if necessary, before plugging the refrigerator back in.