1. Install the add-on
2. Make sure you have at least one File Set. File Sets can be created via the Dashboard > Files > File Sets.
3. Make sure you have at least one Thumbnail Type. Types can be created via the Dashboard > System & Settings > Files > Thumbnails.
4. Add one or more images to your File Set. You can do this via the Filemanager by right clicking on an image and then clicking on "Sets".