Unscrew the electrical panel cover using a screwdriver. Open your electrical panel, find the main circuit breaker, and flip the switch to its "off" position. The main breaker has the highest ampere rating among all the breakers, and is commonly installed on the top of the panel. Turn on and off lights and appliances in the area that you will be working on to test for electrical power. There should be no power in any circuit inside your house because you turned off the main circuit breaker to make it safe to work on any wire.
Pull the two black wires running from the circuit breakers, also pull one green or bare wire slowly out of the electrical outlet box, using needle nose pliers. Get a multimeter and set its dial to 110 volts AC range. Touch the copper core at the tip of a black wire with the metal tip of the multimeter probe, touch the copper tip of the green or bare wire using the metal tip of the other probe, and read the voltage displayed on your multimeter. Perform the same procedure on the other black wire. Your multimeter should not show any reading indicating that there is no power in the wires.
Strip off 1/2 inch of insulation from the end of each black wire and from the green or bare wire, using a wire stripper. Loosen the terminal screws on a 220-volt electrical outlet with a screwdriver. Hook each black wire clockwise around each brass colored terminal screw on both sides of the 220-volt outlet. Hook the green or bare wire clockwise around the green terminal screw on the outlet. Tighten all screws with a screwdriver to secure the connections.
Wrap electrical tape twice around the sides of the electrical outlet to protect and cover the terminals. Fold the wires in a zigzag pattern and push the outlet slowly into the outlet box. Screw the outlet onto the outlet box, using screws provided with the outlet. Turn on the main circuit breaker, and plug a 220-volt appliance into the outlet to test it.