Resizing the product picture on purchase page

I’m setting up a store to sell cartoons and so the “buy” page needs to display the cartoon in a reasonably large fashion, such as 500 px wide. The default seems to be 330 px, which is smaller than desired. I don’t see an area to define the limits of the image that’s displayed. Under media there’s a thumbnail/medium/large set of image definitions but changing those doesn’t affect the image displayed to the left of the buy button. Do I need to go into the actual php code to make changes? I’m using Digital Store with Easy Digital Downloads

https://wordpress.org/plugins/easy-digital-downloads/