The Amazon Kindle does not support the Epub format, so to read Epub books on an Amazon Kindle you need to convert the book to the Mobi format.
Convert from Epub to Mobi
Download the book in Epub format.
Download the KindleGen command line tool from Amazon: https://www.amazon.com/gp/feature.html?ie=UTF8&docId=1000765211
- Open a command line terminal and convert the Epub file to Mobi:
$ ./kindlegen your_book.epub
Send the book to your Kindle via email
Open Amazon’s Manage Your Kindle page in a browser: https://www.amazon.com/hz/mycd/myx
- Find your Kindle’s email address on the Your Devices page
For example: firstname.lastname@example.org
- Send the book to your Kindle as an email attachment