From your Orders page, open Add/edit options, find the Driver tasks card and click Enable, then Add new task and choose the Scanner input type. Give it a name (e.g. “Scan product barcode”) and, if you want it enforced, tick Delivered and/or Attempted to require a scan before the stop can be completed. Save, and drivers are prompted to scan at each stop. Driver tasks are available on Premium and Enterprise plans.
See: Driver tasks · Barcode scanning