Wait until you see ice or frost building up on the inside walls of your freezer. This is a sign that ice is also building up on the freezer's evaporator coils, which means you need to manually defrost the refrigerator.
Remove all of the food from the fridge and freezer. Store it in a friend's fridge to keep it cool.
Unplug the refrigerator and open both doors. Let it defrost for two days. During that time, the ice and frost will melt. If there is a lot of ice, place towels around the fridge to catch the runoff.
Plug the refrigerator back in and wait for it to cool. Put the food back into the refrigerator and freezer.