Once you have logged into your Base account:
Open a listing to edit by selecting the listings option in the menu
Search for the relevant listing either by using the filter, entering the area/street name, or reference number in the search field.
Once the listing has opened click on the media icon
Now click on the edit option below the image and add your desired description, for example, "front view of the building" and click on save
Allow a few minutes for the changes to reflect on your own Flex website and property portals that may take up to 24 hours to update.