How to install a 3-way switch in a home electrical system?

To install a 3-way switch in a home electrical system, first turn off the power to the circuit. Remove the existing switch and identify the common wire. Connect the common wire to the dark-colored screw on the new 3-way switch. Connect the other two wires to the light-colored screws. Install the switch in the electrical box and turn the power back on to test the switch.