This information should be at the top of your manual:

"If you want to have metafield then you should go to Shopify > Settings > Custom Data > Products > Add new rich text metafield. Once the metafield is created please go to Shopify > Products, edit your product and add content there."

on this link: https://help.ecomposer.io/docs/faqs/using-metafield-on-your-store/show-text-from-metafield-in-ecomposer/

it will make it make sense to the content there.

Thank your support assistant "Jennie"