Using Calibre to transfer Nook to Kindle Paperwhite; Livepatch

Hi. I was wondering if anyone knows of a way to transfer a Nook book to my Kindle Paperwhite? When I access Nook through a desktop to read bought books online, I am never given the option to download them; my Kindle has an email address and can receive documents from my two email addresses I have. If I could access the book file, I could simply send it to the nook address.
Using my Android phone, the Internet says that I have to be root to browse to the locations of the book files--I don't want to root my phone. I was hoping there was another way besides risking my phone. Using my phone, when starting the Nook app, the books are presented as the cover of the book to tap on to open the book; when long-pressing on the cover, I can choose "Share", then "Kindle", but when trying this method, I get the error "URL not secure--can only send to addresses starting with https". The internet says that it was reported that Barnes and Noble are going to start using epub, as the Kindle uses. I would rather read a book on my Paperwhite--it's really cool the way they make the text look just like ink on a page.
For my other concern, I was wondering what the use of using Livepatch is? It never seems to do anything--I still have to start the updater to download the updates.o download updates. The computer reports Livepatch is on, though.