Every package in your booking is treated as a separate parcel and gets its own waybill - so each box you want to send must be declared individually in the order. If you're sending several boxes from the same address to the same recipient, you can group them into one multi-piece booking instead of placing several separate orders.
To create a multi-piece shipment, open the booking form and use Add another package in the Shipment section. Depending on the carrier you choose, a single booking can contain up to a dozen packages. Additional services apply to every package in the group, except insurance which is set per package. Multi-piece is not available on inbound (import) shipments.