well, i know how to host and i know how to do it.
1. Go into your router on a website and type your IP (if your router has the default password and account, it should: password: admin. account: admin
2. Click the option to open ports and stuff
3. create a new port
4. type 6112 - 6119 and your computer IP not the router's
5. Turn of Firewall, or just let the Warcraft go right through Firewall.
6. Your Done!
If you didn't understand a thing, i can make a small video to show how i do it, just type me a personal message in Hive =)
Goodluck !