Turn off power to the circuit at the breaker
Verify the power is off with a voltage tester
Remove the switch plate cover
Unscrew and pull the existing switch out of the box
Take a photo of the existing wiring
Disconnect the wires from the old switch
Connect the ground wire to the green ground screw
Connect the hot wire to the common or line terminal
Connect the load wire to the other terminal
If there is a neutral wire, keep it capped unless the switch requires it
Tighten all terminal screws securely
Fold the wires neatly back into the box
Mount the switch into the electrical box
Install the cover plate
Turn the breaker back on
Test the switch
Call a licensed electrician if the wiring is unclear or damaged