You can add an image to a Product when creating the Product, or after the Product has been created.
When you have chosen to add a Product via E-COMMERCE > ADD PRODUCT, you can upload an image as part of the detail.
When you want to add or change a Image on the Product, navigate to the product via E-COMMERCE > EDIT PRODUCTS.
Click the blue image icon to launch the image wizard to add or change the image.
You can add additional images to the product - either via the PHOTOS tab, or by clicking the MORE IMAGES button that appears next to the current image thumbnail, when editing a Product.