You can Add/ Edit Main Images and Images in the Lond Description from Add/ Edit Products.
MAIN IMAGES
Add up to 12 images in this section. Click on the plus sign inside the box to upload an image. Each image should be at least 400*257 pixels.
Learn more here.
LONG DESCRIPTION
Long description describes your product in detail. Give a description of your company and other products here. . The description space allows a maximum of 10,000 characters.
You can also add images, videos, links to the long description. This can be done by clicking on the icons at the top of the long description HTML bar.
Learn more here.