After you finished adding your carrier. Go into Orders -> New, there in the “Action” column you will find the “Ship Order” button.
Press the “Ship Order” and in the new pop-up window and select your courier (we're using USPS as an example here).
Then parcel details or choose a Package Preset, any additional features you may require like Signature or Insurance (options will vary depending on the currier you're using) and finally your Courier Service. Then simply press Confirm Rates and you label will be booked and your Sales Channel order status updated with courier information like the Service Used and Tracking Code.
After pressing Confirm Rates the window will change to allow you to print your Shipping label, Invoice and Other documents you may need.