Of course, you can use Calibre to convert other e-book files as well. When you're settled, click 'OK' at the bottom right. You have a vast array of options to choose from, but for most EPUBs, you should find the basic setup good enough. Calibre should have automatically decided on the MOBI format if you use a Kindle as your primary reader.
Add any EPUB files you've got that you want to convert.
When you first run it, Calibre will ask what language you want to use, and to select a folder to use as your e-book library.Calibre is a free, open-source e-book manager that lets users convert EPUB files to Kindle-readable MOBI files.
If you use an e-reader, it's probably a Kindle, which means it can be a pain to use open-source e-book formats like EPUB.
