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

In this video I will show you how to login into your router/firewall on your home network to allow ports open for your local hosted game server or any other application you need to host outside your home network. Also each open port increases the attack surface of your network, so make sure whatever your port forwarding is secure and don't open ports you don't need open and RDP is never a good idea to have open.
==Hardware/Parts that I recommend==
Netgear router/firewall - amzn.to/3ypLXOa
Computer/Electronics Repair Tool Kit - amzn.to/2HYs46Z
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[@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.