When you have purchased non-Amazon eBooks from other publishers on your computer, you can import them to your mobile or tablet and read them using the free Kindle app for iOS or Android. For example, you can e-mail books as attachments to your Send-to-Kindle e-mail address ([name]@kindle.com), they will be uploaded to your Kindle Library in the Amazon Cloud automatically. You can also send those books purchased and downloaded from third-party sources to your own email address as attachments, then download these books to the Files app on your iPhone, iPad. After that, select the books in Files app and choose the Share option > Send to Kindle, then import them to the free Kindle reading app on your iPhone or iPad. Send to Kindle program for Windows or Mac is another easy way to send your personal documents, books from PC or Mac to your Kindle, Kindle app or Kindle Library.
The above methods let us add our books or other personal files and documents to our Kindle, Kindle app or Library, however none of them can help us send large files which exceed the 50MB limit. Due to the Send-to-Kindle file size limit, we can only send files no bigger than 50 MB. Fortunately we can use iTunes to sync books to Kindle app from our computer which can bypass the file size limit. Here’s how.
Run iTunes on your PC or Mac. We will use iTunes for Windows in this guide. Then connect your iPhone to PC using its USB cable. Press Trust this computer button on your iPhone screen if you see this prompt. Sometimes you may be required to enter device passcode to trust the connection from a computer or allow the computer to access your settings and data on iPhone.
After that you should see the small iPhone icon appears at the upper left section of iTunes on your computer. Click to access your iPhone from iTunes, go to Settings > Apps from the left navigation panel. Scroll down until you reach the File Sharing section on the right panel, choose Kindle app from the app list to open the Kindle Documents.
Scroll down to the bottom, you will see the Add File… and Save to buttons below the Kindle Documents box. Click Add File… to browse to the folder on your computer where the books are saved, select and import them from your PC or Mac to Kindle Documents folder directly. Click Done button, close iTunes, eject your iPhone from PC. Then launch the Kindle app on your iPhone or iPad, switch from Home to the Library tab at the bottom of the Kindle app, you should find the books which you have just added through iTunes.