Assuming you mean how to safely disable an unused light switch:
You will want to turn off the power to the switch at your breaker box. Once the power is off, you can remove the switch plate cover. There will be two screws holding the switch in place. Remove these screws and pull the switch out from the electrical box. You may need to use a flat head screwdriver to release the switch from the box. With the switch removed, twist the wires together and secure them with a wire nut. Replace the switch plate cover and restore power to the circuit.