You need to add a new attribute to your database-backed synced Acme employee record.

Add the new field manually to the ACME_Employee database table and run a database script to resync the Acme employee record.

In the record data model, you add the new field in the ADD SOURCE FIELDS. Save the field with the Update Table checkbox active.

In the record data model, you add the new field with ADD RELATIONSHIPS. Save the newly created relationship and use the field.