Electrical outlets can be installed side-by-side in an electrical box and connected to the same or different circuits. When they are connected to the same circuit, you can connect them together in parallel using short lengths of wire. Outlets are designed so it is easy to connect them in this way. If you do this, plan the circuit so it will not be overloaded by the appliances you plan to plug in to the pair of outlets.
Turn off the power to the circuits you are working on by flipping off the circuit breakers.
Pull the cables through a hole in the back of the electrical box, giving yourself about 8 inches of slack with which to work.
Remove 4 to 6 inches of sheathing from the cables that will be attached to the outlets with a utility knife, being careful not to cut into the insulation of the enclosed wires. Separate the wires and remove about 1/2 inch of insulation from the ends of the covered wires with a wire splicing tool.
Attach the black wire to the bottom brass lug on one of the outlets by making a hook on the end with pliers and hooking it around the screw, then tightening the screw with a screwdriver. Alternatively, insert the wire into the self-clamping hole on the back of the outlet behind the brass screw, if there is one. Connect the white wire to the bottom silver lug in the same way. Finally, make a hook in the end of the bare ground wire, wrap it around the green lug on the bottom of the outlet and tighten the screw.
Use the same procedure to connect the second outlet to the other wire that you pulled into the box, if you are wiring the outlets on different circuits. To wire them to the same circuit, cut a scrap piece of electrical wire about 10 inches long, cut the sheathing and remove the individual wires, and expose the ends with a wire splicer. Connect one end of the black wire to the top brass lug on the first outlet and the other to either brass lug on the second. Connect the white wire to the silver lugs in the same way, and the ground wire to the ground lugs.
Attach both outlets to the electrical box with the screws that are provided with the outlets. Then screw on a four-hole outlet cover.