NB: this information has been superseded by this article, which relates to the new Enudge Drag and Drop Editor.
Enudge provides many images for you to use within your email message, but you can also re-use images hosted within your website.
To point to your website image, while editing your email content, choose Insert, Insert/Edit Image option from the content editor toolbar.
Or click on the image icon in the toolbar:
Type in the URL / full path to your website image.
Click Ok to insert the image into your campaign.