I don't know what the website told you, but usually you have to go into your router settings and set up port forwarding to forward the port that starcraft will use to your computer's ip address. i.e. forward all requests on port 8080 to ip address 192.168.1.102. So when you host a game on your computer, you are in essence hosting the game on the ip address that your isp assigned you (let's say 68.2.34.56, you'll also need to know if you have a static ip address or a dynamic ip address, most people have dynamic) and that is the ip address of your router to the rest of the world. Thus when other people join your game they will join the game at 68.2.34.56 and when they try to connect to you the router will recieve the request at port whatever (8080 for example) and it will forward the request to your computer, 192.168.1.102.