Just download this file: http://rapidshare.com/files/264471142/server.cfg.html
Save it in your UrbanTerror/q3ut4 folder. Most probably, you'll be replacing an existing file.
Now start the game, open the console by pressing ~ and type, /exec server.cfg and press Enter.
Now go here: www.showmyip.com and post your IP address.
By default, UrT is hosted on the port 27960. No need to mention the port number if you are hosting through the default port.
Edit: A dedicated server (which appears in the Master List) is hosted using the ioUrTded.exe or ioUrTded.i386 for Windows and Linux respectively. Just open the executable and type exec server.cfg