If you need it for the Kindle (which doesn’t support .epub) convert it. Just download the excellent freeware Calibre. Then it’s a simple four-step conversion process…
1. Locate and load your .epub file.
2. Select Convert | Convert Individually.
3. Select Convert to .mobi format. No need to configure this, a straight conversion should be fine.
4. Now connect your Kindle’s USB lead to the desktop, then send your converted file as a .mobi file to the Kindle.