After printing and cutting your pieces to fit the box, brush a small amount of Mod Podge or glue onto the box. I cut my pieces so that they are a little larger than the box. This way they will overlap and cover the corners nicely. Once the sides are all glued on leave it to dry over night. You can take and brush another thin coat of Mod Podge over the entire box the next day. You could also spray it with a clear coat of polyurethane instead. Be careful that you don’t smear the colors on your printout, especially if you have an inkjet printer.