hosting Dungeon keeper 2 games

Hi,
I have a Speed Touch 570 with 4 PC's conected, my problem is if I host
a game only computers which are part of my network can join, computers
from the internet can not join. It has be suggested to me that the
router does not know which computer to route the incoming connections
and I need to use 'Port Forwarding', but I can't find this anywhere in
the speedtouch configuration web pages. Can someone please tell me how
can I do this if it is possible? Is this something that can be done
via telenet with the CLI? If so how do I do this as I am not familar
with the commands in the CLI. Another suggestion was that the internal
firewall is blocking the incoming connections and this can be
programmed via the CLI using Telnet. If this is the soloution can
anyone tell me what I need to do here?

Thanx.