Before installation, the update, root or naughty computer system, the best you should create a backup copy to prevent the worst case can occur when the kindle fire hd you can not boot up normally.
How to install Recovery for KDF.
Download this app for: http://www.mediafire.com/?939hty858eoh66p
Copy to KDF and install from the Kindle Fire HD normally as other applications.
Open the newly installed app and select install recovery.
Reboot will see recovery
Now, pick yourself back up to create a backup recovery.