You need to convert these files first, but this can be done for free.
Just follow my instructions below please.
Download and install Calibre on your computer from my link below.http://calibre-ebook.com/
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. Next, select your primary reader.
From the main screen, you can choose to add books by clicking the large icon in the top left. Add any EPUB files you've got that you want to convert.
Select the EPUB files you want to convert and click "Convert books" in the top bar.
Select your options. Calibre should have automatically decided on the MOBI format, if not, select this. Then click "OK" at the bottom right.
It doesn't usually take very long, and once you've converted them, you can send them straight to your Kindle from within Calibre by selecting "Connect/share" from the top right or aiming your device at the correct folder (as long as the Kindle is connected to the computer).
Then you can read the books on the Kindle as they are then in the correct format (.Mobi).
If you have any problems, or would like any additional information or assistance, please do not hesitate to let me know.
And if you can take a second to rate my service, that would be greatly appreciated.