Create a shipment using the order id (entity id, a number) and order item id (item id of the product in the order).
Sample Curl
curl --location 'https://mygatewayurl.com/V1/admin/shipment' --header 'Content-Type: application/json' --header 'Authorization: Bearer nglgsotmwtm67bgs6heqh6czxau8vpdm' --data '{ "entity": { "order_id": 16, "shipping_label": "shipping label", "total_qty": 1, "items": [ { "order_item_id": 16, "qty": 1 } ] } }'