The cover image for a gallery or collection serves as its preview in the Library and on your website. If you haven't chosen a cover image for the galleries and collections on your website, we will automatically use the first photo in the gallery or collection as a preview for visitors to your site.
Setting a Gallery Cover Image
1. Select a Gallery from the Left Pane.
2. In the Center Pane, locate the image you wish to use as your cover image for the Gallery. Click the options icon, and then select "Set as Cover."
Setting a Collection Cover Image
The cover image for a collection may be sourced from any of the cover images among its nested Galleries. To set the cover image of a Collection, select the Gallery that has your desired cover image in your Library, then click "Set as Cover":