Ribbon on product image for "Sales" products

[manolisc]

Hello, I'm trying for the past hours to add a ribbon on the product image. The problem is that in my first try I tried to add a ribbon on all products and the next step was to "select the "on sales products". I'm kinda stuck in the first one. I figured out to add a ribbon but it was backwards of the image.

 

Any ideas?

 

Thank you in advance!