Please help...?

I am running Windows SP2, and have a dsl connection that runs off a router.I have read the forums and it is apparent to me that to get the best download speeds I have to enable port forwarding on my router.It is a marconi 4-POTS Ethernet router.I think I have found the correct place to do this but it is asking me for an IP Address along with the port number. Is there an IP Address that I can put in this required field?

Any assistance greatly appreciated

Sweet Sweet