The easiest way to do it is using the Kindle Personal Document Service:
1. Convert your eBook fileThe Kindle service can't handle an ePub file, only .mobi (but see the end of this article for other document formats supported). You will need to convert it to .mobi format. Here is an online converter that will do it for free http://ebook.online-convert.com/convert-to-mobi
[There may be some formatting issues with the conversion process, but I have not encountered any significant issues with text based books].
2. Find your Kindle email address
- Log in here: http://www.amazon.com/myk (US) or http://www.amazon.co.uk/myk (UK)
- Go to the section that says "Your Kindle Account"
- Under this click on "Personal Document Setting"s. You will see a separate email address for each of your Kindle devices.
You should add one of these to your email address book so you can find it easily next time.
3. Email the file as an attachment to your Kindle account.Just a blank email will be fine with the file attached to it.
Wait a few minutes for Amazon to process the file and add it to your library.
4. Turn on your Kindle device and look for the file.Important: The file will be listed under documents rather than books so you need to look in the documents section.
You may need to re-synchronize or let the file download over wifi.
If it has not downloaded it may be listed under "Cloud" and you will have to click on it to download it to your device.
Additional informationHere is the current list of supported file formats from Amazon.
The Kindle Personal Document Service can convert and deliver the following types of documents:
Microsoft Word (.doc, .docx)
Rich Text Format (.rtf)
HTML (.htm, .html)
Text (.txt) documents
Archived documents (zip , x-zip) and compressed archived documents