SMC router setup

[Joyce Ranieri]

I have a home network with the following configuration:
a 600 MHz iBook with an airport card
a new flat-panel 1GHz iMac connected via ethernet wire
an older 400MHz iMac connected via ethernet wire

All are on an SMC wireless router. Now my question -- How can I 
configure the router so that the 1GHz iMac will be accessible "on the 
road". I'd like to take some of the files off my laptop and leave them 
on the home machine, then access them from work if needed. I know how 
to get into the setup panel of the router by entering the internet 
address -- what I don't understand is what to enter underneath the 
public & private ports in order to "open" them. (I think that's the 
correct word??)

Also, how can I assign a permanent IP address to that computer so that 
it won't change w/ power outages or restarts?

Joyce