you need python (http://www.python.org/) and the pygame module (http://www.pygame.org)
and then run pyNapoleon.py
Have fun!

For those of you who don't know how to play already; an approximate set of rules can be found at http://www.pagat.com/picture/napoleon.html.
This game is based on house rules so it has slight variations but it's essentially the same game.