Method 1: Edit Image on Product Edit Page (Draft and Active page)
Step 1:  Click on the Edit button to go to the Product Edit page

Step 2: Click on "Add Image" to upload a new one, drag to reorder them or delete images by clicking on the Delete icon.

Also you can click on Edit button to modify the image, for example, add a watermark, add a frame to the image, recolor, etc.

Method 2: Edit Image on Bulk Edit Page
Step 1: Select Products > click on Bulk Edit

Step 2:Click on Edit button on the picture

Step 3: Click on Add Image to uploade a new one, drag to reorder them or delete images by clicking on the Delete icon. 
Also you can click on the Edit button to modify the image, for example, add a watermark, add a frame to the image, recolor , etc.
