Look around near the "submit move" button and you will see an option to send a message.
Click that and a dialog box will open.
Enter your message there, then after that submit your move.
edit> The message option is only there when it is your turn to move in that game.
Originally posted by Recklaw How do you message your oponent so as it appears above the game eg: "Hi, good luck" you konw the thing, how do you do it!!!