Step 4: How to put ebooks on your Kindle Fire
Sure, you can buy content from Amazon. I've done it plenty of times myself. And then there are other files that you will want on there such as PDFs or other ebooks.
Here's a total list of files you can transfer over: DOC, DOCX, PDF, HTML, TXT, RTF, JPEG, GIF, PNG, BMP, PRC, and MOBI. One format that is NOT here is EPUB so you will need to convert these to MOBI with a program like Calibre before transferring.
To do this you will need a micro USB cable and it didn't come with the Fire. If you have a previous Kindle, the same cable will work. Otherwise you can get one online for just a few bucks.
to transfer the files over, just plug the Kindle Fire in to your computer and transfer files into the appropriate Kindle folder. So put books in Books, and pictures in Pictures.
Alternately, you can email the files to the email address on the screen. It should look firstname.lastname@example.org. Your email address that is your Amazon.com account will automatically be able to do this. You will need to authorize other email addresses, however.