You can add a new electrical outlet by tapping into an existing light switch's electrical supply. You can install the new outlet anywhere along the wall you choose, providing you can pull the wire from the existing switch. Because of your wall stud locations, you might prefer to add the electrical outlet directly beneath the existing light switch. Adding the outlet at this location can make pulling the wire more convenient, eliminating the need to go through a wall stud or up into the attic with your wire and back down the wall.
Turn off the breaker at the main circuit panel to disconnect the electricity from the existing light switch.
Remove the cover from the existing light switch, exposing the wiring and the electrical switch box. Set a multimeter dial on the 250 alternating current (AC) setting. Touch one probe to one black wire on the side of the light switch and the other probe to any metal on the switch or electrical switch box. The needle on the multimeter should remain at zero if you have properly disconnected the electricity. Repeat this test for the remaining black wire on the side of the switch.
Take out the screws holding the existing light switch into the electrical box and gently pull the switch from the box. Loosen the screws on the side of the switch holding the black wires. Remove the black wire from beneath the two screws and set the light switch aside.
Unscrew the wire connectors holding the two white wires and the two bare copper wires inside the existing electrical switch box. Pull apart the two sets of wires.
Mark the location of your new outlet below your existing light switch at a location that is convenient for you. Trace around the template that was provided with the remodel outlet box. Carefully cut along the trace line with the drywall saw to remove the wall board from the outlet location.
Pull a length of 12/2 nonmetallic (NM) electrical cable from the existing electrical switch box to the new outlet location. Push the electrical cable through a knockout at the back of the remodel outlet box. Push the box into the opening cut in the wall board and twist the screws at the top and the bottom of the box clockwise to clamp the outlet box securely to the wall board.
Strip the outer insulation from the 12/2 NM cable with a dual NM wire cutter/stripper to expose the black, white and bare copper wires at both the existing light switch location and the new outlet location. Remove at least 3/4-inch of insulation from both the black and white wires.
Wrap the black wire around the copper screw on the right side of the outlet and the white wire around the silver screw on the left side of the outlet. Wrap the bare copper wire around the green ground screw located towards the bottom of the outlet. Tighten all three screws and gently push the outlet and the wires into the remodel outlet box.
Attach the outlet to the top and the bottom of the remodel box using the screws provided with the outlet. Cover the outlet, wiring and electrical box with an outlet cover plate.
Twist a red wire connector onto the two original white wires inside the existing electrical switch box along with the white wire from the new outlet, connecting all three white wires together. Repeat this connection for the two original bare copper wires inside the electrical switch box along with the bare copper wire from the outlet.
Cut a 6-inch piece of 12-gauge thermoplastic high heat nylon solid black wire and strip 3/4-inch of insulation off both ends, creating a 6-inch black pigtail. Twist a red wire connector onto the black wire from the outlet, the black power supply wire that runs back to the breaker and the black pigtail wire, connecting all three together.
Wrap the black pigtail wire around one of the screws on the right side of the existing light switch you set aside earlier. Wrap the remaining black wire around the remaining screw on the right side of the light switch. Gently push the two sets of both black and bare copper wires into the back of the electrical switch box and reconnect the switch to the top and the bottom of the box. Replace the switch cover onto the light switch, covering the electrical switch box and the wiring.
Turn on the breaker at the main circuit panel to connect the electricity to the existing light switch and the new outlet.