What are you trying to do?
You can get your external ip by visiting
www.whatismyip.com
Open serverlist.cs in notepad
find
public const string Address = null;
put in your external ip address with quotes instead of null
public const string Address = "you.ip.numbers.here";
then save the file
You should be good to go unless you have a router or a firewall.
Note: you will need to connect by making a local internet connection in uogateway using 127.0.0.1 if you are playing on the same computer that your server is running on.