There are two ways to get files and .mobi books on your kindle. The easiest way is to send the file directly to your kindle through your email. You can also transfer the file via USB.
Here’s how to send to your kindle through your email:
Go to amazon > click on Your Account > Manage Content and Devices > Settings
Scroll down the Settings page to Personal Document Settings.
Beneath this should be Send-to Kindle E-mail settings, and then it says “You can e-mail personal documents to the following Kindle(s) using the e-mail addresses shown.”
On the left, you’ll see your kindle device(s). You may or may not have an email address set up with your device. To set one up, click the “edit” button to the left. And type something you’ll remember. If your email address is firstname.lastname@example.org, you’ll want to type in gee_whiz68 and hit save.
Then you’ll see the email address associated with the device, it’ll say email@example.com.
This is the email address you’ll want to send your doc or ebook file too.
Click open your email, click compose, then copy and paste this email address into the “To:” box. Then attach the file (or drop) into the email, then push send. (You do not need to put anything into the Subject field.) It should land on your kindle within a few minutes. If you’ve waited awhile and don’t see it, push the refresh button on your kindle and go check your document folder to see if it landed there.
This will work with Microsoft Word’s files, pdf’s, and .mobi files, but not with epub files. These basic same instructions are also here: http://www.amazon.com/gp/sendtokindle/email
How to Transfer via USB:
If you don’t have Wi-Fi, there’s a second way, but it’s a little more tricky. You’ll want to plug your kindle into your computer using the USB chord your kindle came with (the one you charge it up with).
An additional drive that says KINDLE should pop up on your computer screen. Click it.
Inside, you will find a file that says “Books” if you have a kindle fire. If you have a kindle paperwhite or an earlier version of kindle, it’ll say, “Documents”. Drag your file into that folder.
After you’ve transferred it over, disconnect your kindle safely.
Feel free to email me HERE if this doesn't work. ;-)