new wrt54g user questions

[Tom Poe]

I have the following:
internet -> dsl modem -> wrt54g -> hub -> 2 desktops

Now, I want to create internal network.  Is it just a matter of changing 
the desktop that represents the internal network to a different subnetwork?
dsl modem = 192.168.0.1
wrt54g = 192.168.0.1??
desktop 1 = 192.168.0.2
desktop 2 = 192.168.0.3

What is the command that will list all the devices on the network?  I 
don't see anything called networkmanager.  Any help appreciated.
Tom