Trying to start a sandbox game for a friend and I.

I’m trying to start up a sandbox game for me and a friend only. I can’t join him for some reason due to me being on a wireless network. Was told I’d have to send a certain port to my router and I have no idea how to do this.

The port was 27015.
Find your router model, and look on
When it asks for a game, search for hl2/css/source

Eh, AT&T installed it when we got their service, but I do know it says 2wire as part of our router’s address

It should be on a label on the router.

Decided to try google as well.