With most protein based stains e.g. body soil, it is important to put cold water on the stain. Heat can actually change the chemical structure of the protein stain, making it much harder to remove. Simply agitate and soak the stained item of clothing in cold water.
Wash the stain under cold water as an initial treatment for the stain.
Then once you have Vanish, follow the instructions above to completely remove the stain.