Use a tape measure to find the height and width of the plate. If it is round, the measurements will be the same. Place a piece of blank paper--2 inches larger than the plate on all sides--on a clean work surface.
Lay the plate face down in the center of the paper. Use a pencil to trace around the plate. Do this on 5 sheets of paper. Remove the plate from the paper and set it aside.
Use the plate shape on the sheet of paper to make a paint design. Use the pencil to sketch in shapes, words, or what have you along the boarders of the plate and in the center. Do this several times, using the fresh sheets for each design idea. Create five paint design ideas with the five sheets, and choose your favorite.
Use the pencil to sketch the chosen design directly onto the plate.
Use small paint brushes to apply the ceramic paint to the plate according to the colors you've chosen and the design you created. Apply a solid base coat of color to change the color of the plate or let the clay show through. Paint a little bit at a time, slowly filling in your design with color. Allow the paint to dry overnight.
Use a small paint brush to apply a thick coating of glaze to the entire front and back surface of the plate. Bake the plate in the kiln according to the directions of the glaze product you are using. Do this to make the plate usable and washable.