Once orders are sent to your shipping software and shipping label are printed, your shipping software create a file with the shipment list and tracking numbers.
You need to import this file in your system to associate the tracking numbers with shipments.
To import the file, select the template in the drop down list and select your file in Import tracking file section and click on Import button.
Once all the tracking numbers are imported, you should see the tracking imported into the Orders to ship section list below.
You have also the possibility to fill manually the tracking number in this list for each order row in the Tracking # column fields, and then click on the Save tracking numbers button.