Turn off the power to the kitchen from your home's circuit panel.
Remove the faceplate cover of an electrical outlet on the wall with a screwdriver.
Remove the screws used to attach the outlet to the electrical box.
Loosen the screws that are used to secure the wires to the electrical outlet. Remove the electrical wires from the outlet and set the outlet aside.
Use a fish wire to run a new electrical wire from the electrical box to the sink.
Open the cover on the garbage disposal with a screwdriver to expose the electrical wires.
Connect the electrical wire that you ran from the electrical box in Step 5 to the wires on the garbage disposal: Loosen the ground screw on the disposal and connect the green ground wire. Twist together the white wires, then twist together the black wires. Place a wire cover over the exposed wires.
Place the wires back in the garbage disposal and replace the cover.
Connect the wires in the electrical outlet to a new switch. Connect the ground wire from the electrical box to the ground screw on the switch.
Twist together the white neutral wires and cover them with a wire cover.
Attach the black wire from the main power to the top screw on the switch. Attach the black wire from the garbage disposal to the bottom screw on the switch.
Place the switch into the electrical box and secure it with the screws.
Turn the circuit back on at the circuit panel. Flip the switch to the "On" position to test the garbage disposal.
Replace the faceplate on the outlet.