1. First use masking tape and tape around the inside of the box around the bottom floor. This will prevent paint marks on the floor of the box when you paint the inside sides.
2. Then paint the sides (both inside and outside) of the box with white and allow to dry completely before continuing.
3. Measure the sides of your box. On this particular box the 2 long sides measured approximately 7 centimeters high and the 2 short sides were almost 8 centimeters. Then trim your paper napkin to these heights. Remove all but the top layer of each napkin piece and place it on the box where it will be glued.
4. Gently apply decoupage glue to the napkin as if you are painting it onto the box. Make sure to apply glue to all of the edges so they will not pull away.
5. When finished, you motif is adhered to the box and you can seal it with a second or third coat of glue to protect it.