Turn off the power at the main circuit breaker supplying power to the outlet to be changed. Using the electrical line tester (according to the manufacturer guidelines), verify that no power is running to the outlet.
Remove the screw and cover plate over the existing outlet to be replaced.
Remove the screws holding the receptacle in the outlet box and pull the outlet out of the box. Remove the wiring from the back of the outlet by loosening the three screws (do not remove the screws).
Pull any excess wire out of the box toward you, to allow easier access. There should be three wires: black (hot), white (neutral), and green (ground).
Looking at the back of the 220-volt outlet, connect the black wire to the top right screw, the white wire to the top left screw and the green wire to the green (ground) screw. If your wiring has four cables, the black and red wire will be connected to the top two "hot" screws, the white wire to the bottom neutral screw and the green wire to the marked green (ground) screw.
Mount the receptacle back in the outlet box using the screws and attach the cover plate to the receptacle.
Turn the power back on at the main breaker. Using the electrical line tester, carefully follow the manufacturer directions to make sure that the power is flowing to the outlet.