Trace the top (twice), front and sides of your box onto your glittered card stock and glue the correct pieces to the box itself.
Glue your second top on the inside top of the box.
Print and cut out your printable and glue to the inside top of the box, onto the glittered paper.
Place a few pieces of tissue paper in the bottom of the box and begin filling your box with unicorn related items. The more the merrier.