Here you are short explanation about downloading and using calibre .

Calibre is a powerful and easy to use e-book manager. Users say it’s outstanding and a must-have. It’ll allow you to do nearly everything and it takes things a step beyond normal e-book software. It’s also completely free and open source and great for both casual users and computer experts.

You can download calibre for your device from this link>>

Watch this video about how to use calibre and get all benefits of it: