You can either chat in the public chat area (everyone will see the chat) or you can send a private message to a friend.

To chat publicly, click your mouse on the thin chat area below the game board. Simply type your text and then hit the Enter key on your keyboard to send the message.

To send a private instant message to a friend in the same game room as you, simply double-click his or her name.

Otherwise, you'll need to launch Yahoo! Messenger to send your message.