Here is how you can add images on items in shop front:
Step 1: Click on 'More' on bottom of the main page
Step 2: Click on Shopfront
Step 3: Click on Items at the bottom of the screen
Step 4: Click on the item to which you want to add image
Step 5: Click on 'Gallery or Camera'
Step 6: Choose the image and complete the uploading process
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