How to remove Digital rights management (DRM) protection from Amazon Kindle ebooks?

Download and install Calibre software.
Download Apprentice Alf’s deDRM plugin from Apprentice Alf’s Blog or from Github.
Open the zip from 2 above and copy the file DeDRM_calibre_plugin\ to your desktop.
Open Calibre, install the plugin.

Configure the plugin by entering your Kindle’s serial number in it.
Restart Calibre, and import your exported book.