Step one: Take a sheet of paper and wrap it around a pencil, taping the ends of the paper to keep the roll from unrolling. Cut the roll to the desired length, keeping in mind that this will form the body of the crossbow onto which everything else attaches.
Step two: form two other rolls which will form the arms of the crossbow, from which you attach a string and launch the pencil from. Bend these rolls back and stick and popsicle stick in one end, then tape them to the top part of the main body part.
Step three: Tie a string to each end of the popsicle sticks.
Step four: Make a paper loop from which you attach onto the body and stick a pencil through.
Step five: Make a small slit in the crossbow body to stick a small popsicle piece through.
Step six: That's about it. Just stick your pencil through the hole in the crossbow, cock the string back, release and shoot the pencil.