How is it related to WE?
Oh, whatever.
1) Open your router (Not physically! It should be in your Network, like any network location if you have a home net, then you'll have router's settings in a browser window), login (Login (usually 'admin'), password (empty or set by you).
2) Go to "advanced" tab.
3) There should be " Advanced Port Forwarding Rules " settings.
3) Make a new rule:
Application name: Warcraft
IP Address: 192.168.0.101 (or whatever your PC has in your local network)
Public Port: 6112~6112
Traffic type: Any
4) Reboot your router and PC just in case.
If you have default settings in your Warcraft (port 6112) then you should be able to host at this point. Make sure that your firewall application or windows firewall does not block your 6112 port as well.
Your router may have a bit different interface of settings (I have D-Link) but you've got the main idea. If you can't follow this guide post here a screenshot of your router's advanced settings, I will try to help.