Place a drop cloth on the floor in the closet's entryway. Empty the closet temporarily to protect clothes and other personal belongings.
Stand on a stool and hold a wall louver vent up against the wall above the outside of the closet. Trace around the vent with a pencil to create a template.
Insert a paddle bit into a drill and tighten the chuck down. Hold the drill bit against the wall, pressing it against the inside corner of the drawn template. Drill into the wall, then repeat on the three remaining inside corners.
Cut out the drywall above the closet with drywall saw or reciprocating saw, using the four drilled holes as starting and finishing points.
Insert one side of the wall vent into the outside of the closet, then insert the other half of the wall vent into the inside of the closet. Clinch the two together with a screw gun, pulling the two sides tightly against each side of the wall.
Remove the stool and drop cloth. Vacuum out the closet to clean up and then put your clothes and other belongings back into the closet. Your closet is now vented and won't be stuffy any longer.