Yeah, opening a port isn't trivial, especially if you've never tinkered with it before. It must be allowed by the router, OS, and any firewalls you might be running.
The reason why the instructions are somewhat vague is because the process is different for everyone depending on their os/hardware configuration. As the guide alludes to, you should find your router and follow the detailed instructions for opening a custom port:
http://www.portforward.com/
If you get stuck at a specific point, pm me and I'll try to help you through it.