At first, make sure to install Editorify App. Here’s the installation link: Editorify App
Browse your store & find the product you would like to edit. Enter the product page and click the "edit" button that appear on the top left corner.
There are two situations where the add button might not appear :
1. Please check that Editorify app is installed correctly
visit your admin page/apps and check if Editorify is installed.
2. if you're using your own domain, please Login to your admin panel, go to online store/ domains, make sure your primary domain include "www" , when done click on the arrow on top left screen.