Ok So......
... ..
https://en.wikipedia.org/wiki/Port_forwarding
It one heck of a read, and too much to explaine here. However if you for some reason want to bore yourself lol, there is the link.
I wouldnt try any of that bud, Its a lot of "pull your hair out" unnecessary stuff.
But most all routers have a “reset” button embedded on them. So if things get weird, just reset and start clean.
If you do want to play with it, make sure it has a reset. SHOULD be a small pin size hole.
If you can get online the game, port forwarding isnt the issue.