The PP is correct. By default Amazon will register a kindle to the Amazon account that purchased it unless they indicated it was a gift. You need to de-register it from that account and set it up on your own.
Assuming you have the WiFi set-up on the Kindle
go to the Home Page
Make sure where it says "DeRegister" is underlined
Click the middle button from the 5-way controller
Then you can either register it to your account via the Amazon webpage or the Kindle itself