Pry off the metal prongs at the bottom of the zipper, using a screwdriver or pliers.
Hold the two sides of the zipper next to each other at the bottom, as if your were zipping up your coat. Slide your zipper pull onto the bottom teeth of the zipper.
Hold one hand against the bottom of the zipper and use your other hand to slowly draw the zipper pull upward. Your zipper will close as normal. However, if you pull apart the sides of the zipper, it will all fall apart.
Use a pair of needlenose pliers to widen the zipper prongs that you removed in Step 1. Slide the prongs onto the bottom of the zipper and tighten them by squeezing them between your pliers.