Hi,
To embed images, you first need to upload them to a web server, as they have to be present each time a request is made (a page containing the image is shown).
If you have a web site, you can store the images there, if not, services like Photobucket or similar can be used.
If the file only exist on your local hard drive, you can use the attachment function (Click on the link under the text field and browse your way to the file). This will upload the file to the SoR server and place a miniature and a link after your text.