To send a message to your opponent, simply type your message text into the first line of the box on the lower lefthand side marked 'Out Window', and press the button (on the right hand side) marked 'Msg'. The 'Out Window' may be cleared at any time by striking the 'Enter' key.
To receive a message, just keep an eye on the 'In Window'. Both moves and messages will be displayed there. Messages will have the letters 'MSG' at the beginning. A distinctive tone will announce the arrival of a message from your opponent. The 'In Window' may be cleared at any time by striking any 'Arrow' key.