Arrange the napkins on the canvas until you are happy with the design.
Remove the napkins a few at a time and apply decoupage medium to the canvas with a sponge brush. The medium should completely cover the canvas, but not be excessively thick.
Press the napkins into place slowly, eliminating any air bubbles or wrinkles immediately.
Continue until all napkins have been pressed into place. Allow to dry for at least 30 to 45 minutes.
Apply a thin coat of decoupage medium on top of the collage of napkins using a light touch with a soft sponge brush. Allow to dry for at least a half hour and add another thin coat.