To view Custom Fields, go to the Products module and select the product. Go to the Custom Fields tab.

Select Edit and update values in fields as applicable. Each business will have their own Custom Fields with their own definitions for use. 

Save to record changes.

Settings

For users with the required permissions, Custom Fields can be updated from the Products \ Custom Fields screen by selecting the Settings button to go to the Custom Fields Settings screen. These can also be accessed form the Settings \ Products \ Custom Fields menu. 

All Custom Field options display and are available to edit. New fields can be added and existing fields that are no longer required can be deactivated.

Refer to Settings | Custom Field Settings  for more information.