The process is very simple: 1) Hover over the Inbox link at the upper right. 2) At the bottom of the dialog box that opens, click on the Start a New Conversation link. 3) In the Participants box, start typing a username. A list of possibilities will appear and you can select from the list. 4) Give the conversation (message) a title. 5) Type your message. 6) You can add a file if you want (Upload a File button) 7) Click the Start a Conversation button.