If you haven't already, switch to the Xfire Shadow skin (it has a textbox entry to join specific chat rooms) and in the "Chat Rooms" tab, go the the bottom where the text box is and type in:
man this thing itches
Then click on the Enter Chat Room button (the big green arrow) and voila. When you do that, there'll be a popup asking you if you want to join the voice chat server, so click Yes and you're good to go. Once inside the chat room, click on Actions -> Save up top of the chat window to save the room incase you want to join in the future with a double click.
Or if you want less of a hassle, just find one of us on Xfire and ask to invite you into the chat room
If you have a mic that you want to use, it's usually a good idea to bind voice chat activation to a key.
- In the main Xfire window, click on Tools -> Options.
- Go to the Voice tab and make sure "Push to Talk" is selected and click on "Set key binding" to bind it to a key. Since you'll also be using this key ingame, make sure it doesn't conflect with a hotkey you use in Demigod.
You should be good to go by then. If you have any problems or questions, feel free to ask any of us on Xfire or on here and we'll help you as best as we can :]