In order to write a note, you need a piece of blank paper (often available at your local grocer) and a quill pen. You need to "hold" the pen and then "write note". To read the note, you need to "hold" the note and "read note"
To write a message on a bulletin board, use WRITE <subject> in the room where the board is. You may also want to REPLY to the last message you read.
This command will take you into your chosen editor (from CHANGE EDITOR). For the standard line editor, you may exit by entering %e on a new line.