All Asset Tracker devices are intended to be used in a product, not as developer devices. This makes it easy to manage a fleet of asset trackers, allowing per-fleet and per-device configuration settings, and features like fleet mapping.
It's OK if you're starting out with a single Tracker; you can create a free prototyping level product that only has one device in it. From the console, click on the Products icon (1) then New Product (2).
When you create the product, be sure to select Asset Tracker (Cellular as the type.
You can reuse this product for more than one tracker device, you don't need to create a separate product for each device.