To use your silkscreen: Lay the silkscreen on your slab of clay, shiny side down. Using a roller or your hand, make sure that the screen is making 100% contact with the clay, but do not press the silkscreen down into the clay, which will ruin the silkscreen. Squeeze a line of medium-bodied or thick-bodied acrylic paint (I like Liquitex) on one edge of the silkscreen. Using an old credit card or something similar, pull or drag (do not press) the paint across the surface until you have full coverage. Immediately clean or you will ruin the silkscreen.
To clean your silkscreen: Place the silkscreen in a shallow dish of water or rinse off immediately so that the paint does not dry and clog the openings in the silkscreen. Gently wash (do not scrub) the silkscreen off and let it dry flat before using it again.