You'll need to head over to the Amazon website and sign in first.
You'll need to look up yours, as you're not told when you set up your Kindle, but it's little hassle.
If that last clause makes no sense, don't worry - not many people know, but your Kindle has its own bespoke email address, using which you can send files to it. To get a PDF on a Kindle, you're going to need to know your Kindle's email address.
