How can I set up combined shipping?

Only products that have been set with "unionDeliveryType": "UNION_DELIVERY" during product registration are eligible for combined shipping on Coupang.

<Combined shipping criteria>
- Only products with identical shipping location info are eligible for combined shipping.
Mandatory to input outboundShippingPlaceCode (shipping location address code).
- Combined shipping is not available for "pay upon delivery" shipping fee option.
Need to set to either pay in advance or free delivery.