Originally Posted by Mike L
Solicitous is completely correct. You just have to register your Kindle to your Amazon account. To do that, you need to know your Kindle's serial number (not the same as its PID). The serial number is printed on the back of the device.
Thanks, Solicitous and Mike. I bought the Kindle through my Amazon account, and according to the manual this should have registered it automatically. But it didn't, so I'll follow your advice.