If you're checking out online, you can add the PO number for your order in the Apruve check out modal:
Once this has been added here, the PO number will be reflected on your invoice.
If you're placing an order offline with your sales representative, tell them the PO number for the order and it will be included in your order information and invoice.
If you forgot to add a PO, email support@apruve.com to add to an existing order/invoice.