The youtube tutorial series goes into how to do it on a local machine, but I can’t find any documentation on how to do it if you want to set up something that you can connect to over the internet. I understand how to configure routers, and the like how I need, but I need to find some documentation on how to configure the actual game server.
This page on the wiki describes how to do this. If you start the game with one of those command lines (listen or dedicated) you’ll be able to connect over the internet, assuming your router is configured. Usually this involves forwarding port 7777. This post also has some more information.