How do I get books from my Kindle to show up in Calibre Companion on my iPad? My friend has shared her library to my Kindle and I want to use Calibre Companion to store my library and metadata.

The short answer is: you can't, *unless* your friend has all her books without DRM (Digital Rights Management), since Amazon, as a rule of thumb, protects all their eBook sales with DRM. The exceptions are free books, that either the author gives away, or that have expired copyright (i.e. those downloaded from Gutenberg.org or Archive.org). This essentially means that those books are encrypted and thus cannot be read directly. Your only choice is to use the Kindle application on your iPad... that is the only legal way of doing so.