You just need an Amazon account. You can download direct on your PE using the Amazon app -- oh! I got the app to my PE through email from Amazon (which is probably why you asked the question in the first place -- doh!), and I don't know whether you can have them send you the email and then sideload it somehow.
Is there a reason not to set up your email? If you have the info you need it is pretty easy and straightforward to set up, IMHO.
Sorry -- I see I'm not much help after all. <sigh>