Once a reservation is fully or tentatively completed, you will have access to the Case Notes in your Case Tools menu. This is the sidebar on the left hand side of the screen. Simply click on an icon to open up the full menu.
Under Case Notes, you can leave a private note, not visible to the buyer, by entering the details into the text box. The user who left the note will be visible and will show the date/time it was submitted also. These notes can be edited and also deleted.
You're also able to leave a note via cc'ing the email address listed in the Case Note also. In this instance, the company name will display and not a specific user, and these cannot be edited or removed.