How do I add a picture to a product listing?

Select Products from the left hand navigation panel. Click on the three stacked dots next to the product you’d like to add a picture to. Click Edit.

This will open the product editor. Locate the Photos section, and either drag the picture you’d like to add to the product listing from your desktop, or click "Browse Photos" to browse for the image. 

Click the blue "Save" button at the bottom right of the screen to save the image to the product page.