The help topic for adding an image is missing some important information.
The page that shows up in Help is https://dancestudiopro.zendesk.com/hc/en-us/articles/4404671632397--How-do-I-add-an-image-to-a-Robo-Mailer- It says "In the popup, paste the full URL of the image you want to include in your email."
Well, that's not really what's needed. You first have to (1) add it to a webpage and make sure it's published. (2) Go the page on the web. Here's what's missing. You don't just copy the URL. You have to right-click on the image on the website to get the URL.
We've clarified this help article - thanks for letting us know!