Most of these are the same instructions you can find on the "noWON CS1.5 server" page over at No WON. I have simplified, reorganized and rephrased them so that (hopefully) they will make better sense.
Once you've followed these instructions your server will be accessible from the internet via the WON2 network. Be sure to patch your client with the No-WON / WON2 Patch for Playersthen use the in-game browser to find your server.