Remove the plastic handle (may have to pry off the C cover, and remove the screw), remove the silver escutcheon by turning counterclockwise, and then get a set of faucet wrenches from Home Depot (typically 5 or 6 deep sockets and a handle on a safety pin shaped wire). One of those should fit your valve. Remove the valve, and look for a washer screwed on to the bottom of the valve. Replace that rubber washer and screw. Put your finger in the hole, and feel the valve seat to see if it is smooth. Of not, replace the seat or get a seat grinder, and grind it smooth. Reverse the steps to reinstall the valve.
