Click on one of the folder icons to view the images from a specific gallery.  You can view larger versions of the thumbnails by clicking them.  While viewing the large version of an image, hovering to the left and the right side of it give you the option to see the previous/next image in the sequence, respectively.

Click on one of the folder icons to view the images from a specific gallery.  You can view larger versions of the thumbnails by clicking them.  While viewing the large version of an image, hovering to the left and the right side of it give you the option to see the previous/next image in the sequence, respectively.