I had a hard time figuring this out but when I did, I smacked myself with a spike. Just kidding.
If you're running Parallels on your Mac, the first thing you need to do is make the IP Address on your Mac match the IP Address on Parallels. Normally Parallels grabs a different IP but you can change that.
Up in the top, click 'Virtual Machine' then at the bottom of the drop down, click Configure.
You're gonna want to go to Network (it might say Network 1 or something - doesn't matter), and choose the type of internet you have. Make sure you choose one of the choices listed under 'Bridged', then check the box that sends Mac address to DHCP server.
Now, you need to setup portforwarding. There are lots of tutorials out there for that. It's pretty simple.
Have fun hosting!