How can I host a Listen server, for Garry's Mod?

Well, my friend recently received Garry’s Mod.
So, besides looking for a server every time we want to play, I finally decided, I want to host a server.

I need help trying to open ports properly, and how to configure anything else.

Pictures of my Ports below.

So, any idea why is won’t work when ever I try to host a listen server?

EDIT:
If you want to know my router model, it’s WBR 1310

68.3.162.187 is your public ip (the ip you give to your friends so they can connect), the ip you need to put in is your private ip (something like 192.168.0.X).

It’s 192.168.0.102, I found out.
So, I replaced it with that, what next?

-bump-

That’s good.