Shut off the water line to the home. This is typically located outside near the water meter. Turn the handle clockwise all the way to shut off the water. This prevents you from accidentally turning the water on while you work and getting soaked.
Locate the screw that holds the bathroom faucet in place. This is usually located under the faucet. Use a screwdriver to loosen the screw then remove it.
Pull the faucet away from the wall by gently moving the faucet toward you. Remove the rubber washer from the pipe behind the faucet and set it aside.
Use a wrench to loosen the diverter valve from the pipe behind the faucet. The valve will be located directly behind the rubber washer. Pull the diverter off of the pipe. Slip the new diverter onto the pipe and tighten it in place with the wrench.
Place the rubber washer back onto the pipe and slide the faucet over the washer and the pipe. Insert the screws back into the faucet and tighten them with the screwdriver.