Software updates automatically download and install for Kindle Fire HDX 8.9" customers when connected wirelessly; however, you can also manually download the software and update your device via USB cable.
Before you perform these steps, make sure you determine your software version.
Important: You may need to download and install additional software on your computer before you can transfer content to your Kindle Fire.
Mac computer with OSX 10.5 or above - You will need to install Android File Transfer, a free application, to complete the USB transfer. To download Android File Transfer, go to http://www.android.com/filetransfer.