Print out the template of your choice (Boo, Pumpkin, Cat, Haunted House, and Ghost) onto cardstock. Cut out the rectangle portion of the card. Using the ruler, score the dotted lines with the back of the X-acto knife blade, then cut along the solid lines.
Flip over the card so the printed side is face down. Fold along the scored lines.
Score and fold a 6-1/2-inch-by-9-1/2-inch piece of cardstock in a contrasting color. Use a glue stick to glue the pop-up card to the second piece of cardstock.