Instructions
To Send a Message
Press the ALT and C keys simultaneously on your keyboard. This will display the Xfire overlay interface.
Double-click on the name of one of your friends in the Xfire Friends list.
Type your message and press the Enter key on your keyboard to send it. Press ALT and C again to return to your game.
To Receive a Message
Press the Scroll Lock and X keys at the same time on your keyboard when a friend's message pops up in the lower-right corner of your screen.
Type your reply in the box.
Press Enter to send your reply to your friend.