The video below shows the process of move an image to the shopping cart (click the button on the bottom right of the video to expand the view). You can also follow the screen shots and steps below this.
You need to make sure that when uploading an image to the Toolkit that is to be added to a product / shopping cart page, you select
"Product Images - e.g.Website Shopping Cart".
To move an image to the products gallery simply do the following: