You've created some user extensions, your phone is plugged in, but you still see "Unassigned" on the screen. What's next?
Click on Business Phone - Device Inventory
Click the drop-down menu beside one of your phones to select a user to be assigned.
The phone should reboot in the next minute or so, initialize and you will now see your user's name and extension number on the screen.
You can assign a user to multiple phones in your device inventory.
The result will simply be that those phones will all ring simultaneously when a call is directed to that extension. Outbound calls will display the caller ID and name that was configured in the user settings.