How to setup Host for remote access

[GMSIRK@cs.com]

Hello

I am not sure how to setup host (server)
Here is what I do.
Install the server. Make it run
Assign password.

It gives me a local IP address.
I need an address so that it can be accessed
remotely.
With the server running  I call up

http://www/realvnc.com/cgi-bin/nettest/cgi

It returns an IP address  and port 5900

Is this the address to use when calling this 
server remotely?
Does this address remain constant for this location?
( I also notice that it returns same address for
  all computers on the same modem)
I have trouble testing this as I only have 1
ISP available.
(In other words I have trouble calling myself)

Is there a walkthrough that I can follow?

Any suggestions would be appreciated.
Thanks

George