Orders are processed on the specific marketplace where the item was sold. It is inside the marketplaces seller portal where you will handle shipping and completing the order.
Mascot Network orders are different: you fulfil them in Mascot. Go to Sales History, open the order (lightning bolt icon) and click Print Shipping Label. Don't contact the marketplace; message Mascot Support for cancellations or tracking changes. See Mascot Network Orders: shipping, cancellations and what to do if something goes wrong.
You can use Mascot to review all sales in 1 screen (Sales History), mark the invoice as shipped when complete, and review the accounting details.