How do i do that? Can you send me a link to some sort of video that explains how its done or a guide itself will work i guess. TY!

I'm talking about bo2 primarily but it doesnt work on both. i was in a game with a wepaon all the time even though i have tried in a lot of different ways. Are u talking about this. By the way, im spanish so u i guess u wont tell what's happening:
https://gyazo.com/2fc3409440f58d3c772c5aaeac461776.
Did all of the thing in this tutorial: https://www.tomshardware.com/news/how-to-open-firewall-ports-in-windows-10,36451.html.
Thank you again in advance. And sorry for not knwing where to upload this thread.

I have already tried to do what this "Custom Games / Playing with friends#" has explained me. I have tried with UPnP which is enabled rn and with the port forwarding. Nothing seems to work. It is always the same, few seconds trying to load but never gets in the game with my friends. Any real help on this problem?. By the way i have tried to do it with hamachi to but it doesnt work. Thank for your time