How to port forward ports from router to computer for game server or any application

[@SirDemon61]

How do I know what to put in for the "Alternate DNS server"?

[@SirDemon61]

Im hosting a 7 Days To Die server and found your video on the game very insightful but now I have a friend that wishes to join and they type in the same information that I use to log in and it gives them an error. Saying they cannot connect. Even tho I login just fine. I found my routers Preferred DNS server address but can not find anything about the Alternate DNS server address.