Absorb's email message templates allow users to add an image by clicking the right-most icon in the editor's format bar. When you click this, you'll be prompted to enter a URL for the image you'd like to add.
This link can be to any image on the internet that is publicly accessible. There are several free image hosting solutions out there that will generate such links for you, but you can also grab one pretty easily using files uploaded directly to Absorb LMS.
Open up the File Manager and upload an image from your desktop to your Absorb LMS file directory Select your file and click the preview button to open that file in a new tab Copy the link in the address bar of this new tab Paste that into the URL field when adding an image to your message template.