Make sure the water is isolated (shut off) take the top off the tap (plastic cap) take the screw out and pull the body of the tap off. Get a spanner to fit the nut (about 24mm or an adjustable) turn it anticlockwise steadily, holding the spout of the tap to stop it going with it. The whole body of the tap will now seperate and you will find 2 washers. put them on as you take them off. Check that the tap is moving correctly and reasemble.
Ressy, December 2009