Variant Image Penguin: Container Selector Identification
This site should help you identifying the name of the container your theme uses to display the thumbnail images. This is part of the initial setup in the app settings page:
This part can be a bit tricky and you should be familiar with HTML basics.
To identify the relevant element for your page, you can inspect the elements with Chrome/Firefox. Look out for the element that surrounds your thumbnails (NOT the main image), the one which is the first common ancestor to your thumbnail images.
This element will have a class or an ID which you should copy over to the settings area. In case it is a class, please add a dot before the name, e.g.:
If the container has an ID, you should add a hashtag, e.g.:
The default setting for the thumbnail container is: