Turn off the breaker, naturally. Plug a light into the original outlet to make sure you have the right one. Try to pick the same gauge (I assume you mean indoor) wire. It has to be solid wire. DON'T USE ANYTHING ALUMINUM. A small razor usually splits the insulation lengthwise and allows you to separate the wires. Wrap the ground wires (usually bare) tightly together with a pair of pliers. If you can't reach the group add another piece to the group first then extend it to the ground on your outlet. The BLK+WHITE should be stripped, be careful not to nick the wires, according to the length guage- usually found ingraved on the back of the outlet. If you're lucky there will be an extra set of holes in the back of your present outlet and you'll be able to simply push them in. Black must go on the same side as the other black....[note white screws, actually silver, means white wire, and brass colored screws are the black wire side] Usually when I put in a new outlet I replace them both. Don't go too cheap. Running the wire to the second outlet will be the biggest challenge. That's more than I can type in this response. Good luck. Check a hardware warehouse for the proper style of indoor wire and some safety tips. Buying a cheapie outlet tester wouldn't hurt either..it has a series of lights that indicate all is well before pluggin something in...about $10.00