Sorry, you need to have your images already available on the WWW so that they can be referred to by an URL.
For example, the image at this URL:
http://boku.smugmug.com/photos/28511517-M.jpgcan be loaded into this message by clicking on the "Image" button when composing and putting the URL into the dialog box. When the message is displayed, the viewer's browser pulls the image from the website reference:
