If you have an order whose label was not printed through ShipStation (say, a local delivery or a digital product), you can simply mark the order as shipped in the app.
To do this, find the order(s), and click on Other Actions, and then choose Mark as Shipped.
On the Mark as Shipped popup that appears, enter the tracking number in the Tracking# column (if none is needed, carriers Other and USPS allow tracking number(s) to be left blank) and specify Carrier, adjust Ship Date, and click Notify Customer?, Notify Marketplace? & Allocate Inventory? as needed (if you click on the blue header for each column, you will be able to bulk apply the given choice to the entire order list).
Finally, click Mark as Shipped! and the orders will move into the Fulfillments on the Shipments page.
Here, you will be able to track your shipment's progress to the recipient as you would with a shipment that was processed in ShipStation. (Keep in mind, orders marked as shipped count towards your subscription's monthly shipping limit.)
Please note that you may get errors using this feature with ChannelAdvisor. Please make sure you have followed the steps to set up your carriers correctly in ChannelAdvisor.