The following wires are required for a multi-switch installation. Refer to the instructions with your add-on switch for a common way to configure your wiring.
Line (hot): Black wire – supplies power
Load: Black wire – connects to light
Neutral: White wire – can be a bundle of wires in the back of the switch box
Traveler: Often red but may be other colors – connects device to another switch location; required for three-way installation
Ground: Green or bare copper wire