Common:Adding Images to Templates
In HTML, an image is referenced using a tag that has the form: <image src"...">, where the src attribute contains an absolute or relative path to the image. That path can be a file path like ../images/local_image_file.jpg or it can be a URL of the form http://....
When the email arrives in a recipient's inbox, file paths are obviously of little value. (They would only work if recipient happened to have all of the right images at the right locations on their local system. Small chance!) So Http URLs are used to access the images.
__TBD: This has changed. After uploading, use the short URL for the image.__
To generate those URLs, the images to be included in the URLs need to be uploaded to the platform as Public Documents. URLs for those images become available when they are made public. You then insert those URLs into the <image src"..."> tags.
The resulting tag as the form <image src="https://{yourDomain}/networking/...">. The link then works in the recipient's email, because the image is publicly available.