Navigate to the Settings menu and then click on the Products tab to access fundamental configuration options.

Settings > Products

You will see Enable Sheet Formulas at the bottom of the page. Click on the toggle switch to turn on sheet formulas.

Now you can start using Google Sheet Formulas such as SUM() or AVERAGE().

Note

When you turn on Sheet Formulas, the Thumbnail and Image columns will only support Image URLs of products. If you have had seen or used IMAGE() forumla in those columns, they will be automatically converted to URLs when the toggle switch is turned ON.