You have to choose between a static IP given by the router or a dynamic one (DHCP) that will change sometimes and make port forward useless.
I copied a part of one of my old post:
To get a static address (much better for setting port forwarding):
http://www.portforward.com/networking/staticip.htm
To open port 6346 on router and make port fowarding:
http://www.portforward.com/routers.htm
This site is great and much more efficient that I would be explaining things once by once to you.
Bonne chance
