Here’s a basic explanation of the wiring of an outlet.
If you’re wiring a new outlet, pry up and remove the round knockout, where the wire will enter the box, and loosen the screws on the clamp inside. Until the cable is inside the box, the white sheath should cover the three wires. Once the cable’s inside, you clamp it so it can’t easily be pulled loose, and remove the white sheath as far back as possible toward the clamp. Use a utility knife, being careful not to remove the individual insulation on wires.
Now, pick up the receptacle. You’ll see two screws on either side.
The brass-colored screws are the hot terminals, and you should connect the black wires to these. (Test for hot wires with a circuit tester to make sure the black really is hot.) The silver screws are for the neutral wire (white). And the odd screw at the bottom (often green) is for the ground (bare) wire.
Now, technically, you could screw the hot wire carrying the power to one brass terminal, and then continue on to the next outlet from the other brass terminal. As long as the metal tab between them hasn’t been broken, this will supply this outlet with power and carry power down to the next outlet. Same with the neutrals.
However, it’s usually best to “pigtail” the wires. This means a short length of wire comes from the terminal and connects to both the incoming wire and the outgoing wire. This way, if the receptacle becomes faulty for any reason, you’ll still have power and the safe return of electricity.
We’ll show you how to do this next time.