Without wanting to sound like a boring old fart, or being age-ist, perhaps you require some assistance from whoever-setup-your-network?
Sorry if I'm already stating the obvious, or talking down at you but (I've recently come across a number of people who have done this, for other games, caused problems and got into trouble from advice on forums [and I have no wish to see it happen to you]); when you run a server you're basically allowing people to remotely connect to your server PC; be it your PC, or a dedicated machine. Unfortunately when you're behind a router you need to forward some ports, so that they connect straight to your PC, instead of trying to connect to the router (which it then blocks). If you mis-configure it, it can be "dangerous".
For reference, the ports you are required to open / forward are:
TCP/29339, TCP/63392 and UDP/63392
The steps are different, depending on the make and model of the router you use, I'm afraid. The usual steps are to goto its IP in a browser, login, goto Port Forwarding and then follow the instructions on-screen.