The pink i button and new file button referenced are features of the free addon Image Handler 2 (http://www.zen-cart.com/index.php?ma...roducts_id=117)

To add additional images manually, here is the tutorial: https://www.zen-cart.com/tutorials/index.php?article=58 :)

Oh and edited to add...the 'additional images' on the page you linked are actually the attribute images which would have been uploaded from the Attributes Manager