To treat stuffy noses with Vicks Vaporub you place a little bit of Vicks Vaporub in each nostril which helps the stuffy nose.
You can also put the Vicks Vaporub directly below the nostrils if you don't want to put it inside your nostrils.
Either way will work since you'll be breathing the Vicks Vaporub in through your nose.
Another great way of treating a stuffy nose or other congestion is to place some Vicks Vaporub in the water of a vaporizer and breath in the steam.