Adding my own photo to a listing

DagsBricks

I've got an applied sticker across assembly (STAMP) that I've got listed here. The default image is the entire sticker sheet. Despite my description of which sticker it was and the condition, a buyer did not read that and ordered. When I inquired to make sure they knew what they were getting, they eventually declined the piece, which is better in the end. I couldn't help but think that it would be helpful if the buyer could see exactly what they were getting.

How do I upload my own photo for a listing?

Brian