Unplug the fridge to prevent any electrical shock during the operation.
Examine the feet of the refrigerator. There will be a large hex screw near each foot. This is the adjuster screw that will lower or raise the height of that particular foot.
Open the refrigerator doors and place the level on one of the shelves.
Turn the adjuster screw with your socket wrench. Most screws take a 3/8-inch socket. Turn the screw clockwise to lower the foot and counterclockwise to raise it.
Adjust each foot as needed. Examine the level periodically until it shows that the fridge is leveled properly. Plug the fridge back in.