Description, Addition Information, Review is auto show the data from the Product description, product variant and review app
If you add the new custom tab so you can edit the content
To edit Description tab, you need to go to Product and write the content to Product Description, if you want the layout same as our demo, you can use this HTML: https://codepen.io/TeaThemes/pen/XzOvLL
and paste to HTML mode from the product description: http://prntscr.com/j0ihvz and change the content.
You can also see another HTML