Wash the dish with warm water and soap. Dry it with a dish towel.
Dip a cotton ball or clean rag in rubbing alcohol and wipe the dish with it.
Open a jar of paint and squirt it into a paint holder. Use nontoxic paint designed especially for cookware if you intend to use your dish for eating food. Use enamel, glass or acrylic paint if you intend to use the dish as a decoration.
Tape a stencil to your plate if you wish to paint a very clear, specific design.
Dip your paintbrush in paint and run it across the dish until you have painted the entire area. Dip the brush in water to clean it and add any other colors you desire.
Allow the paint to dry for several hours and remove the stencil.