Select Get to download and install, or Update to update the Kindle app. Search "Kindle." From the search results, select Kindle. Use the Kindle app to start reading from your devices.
All accounts that use your current Apple ID need to be signed out of.
So will iPad mini 4 and all its predecessors except the first generation one.
How to update / restore your iPhone/iPad/iPod using the downloaded IPSW file: 1.