How to add Kindle (.mobi) files to a Kindle, iPhone or iPad
Adding Kindle eBooks to a Kindle Reader
eBooks purchased from Echo Books are easy to add to the Kindle using a USB cable. To add a Kindle book (".mobi" format) to your Kindle:
1. Turn the Kindle on.
2. Connect the Kindle to your computer using a USB cable. You should see your Kindle appear as a disk drive or folder on your computer.
3. Drag and drop the '.mobi' Ebook file from your computer into the 'Documents' folder on the Kindle drive or folder on your computer.
4. When the USB activity indicator on your Kindle stops flashing, 'Safely Remove Mass Storage Device' (Windows) or 'Eject' (Mac) the Kindle from your computer.
5. Unplug the USB cable from your Kindle. The Ebook should now appear in your Kindle library. If you can't immediately find the book on your Kindle, switch the Kindle off and on again. It can take a few moments for the new eBook to appear on the Kindle reader.
Adding Kindle eBooks to an iPad or iPhone
You will need to have downloaded and installed the Kindle App on your iPhone or iPad to make this all work.
1. Connect your iPad/iPhone to your computer via USB cable.
2. Launch iTunes 9.1 or later on your computer (where the eBook was downloaded).
3. In your computer, in iTunes under 'Devices', on the left, select the iPad or iPhone which is where you want to read the book.
4. Select 'Apps' from the top Menu bar of iTunes.
5. In the Main Panel, go down to the 'File Sharing' list.
6. Select the 'Kindle' App.
7. Drag the Kindle (.Mobi) eBook file from your computer into the 'Kindle Documents' box that is on the right of the 'File Sharing/Apps' list.
8. The Book should now appear on your iPhone/iPad when you open the Kindle App.
9. Read more here: http://support.apple.com/kb/HT4094#