Turn off power to the circuit at the breaker box
Verify the power is off with a voltage tester
Remove the switch plate cover
Remove the screws holding the existing switch
Pull the switch out of the electrical box
Take a photo or note the wire connections
Disconnect the wires from the old switch
Connect the wires to the new switch in the same positions
Tighten the terminal screws securely
Fold the wires neatly back into the box
Mount the new switch into the electrical box
Install the switch plate cover
Turn the power back on at the breaker
Test the switch to confirm it works