The above video show you how to unbrick and flash Amazon Fire OS back with Stock Recovery.
You can easily return to stock FireOS. You may need to do this if something goes wrong when installing Cyanogenmod.
Steps:
1. Download FireOS 5.3.1.0
2. Download and run ADB Installer
http://forum.xda-developers.com/showthread.php?p=4891511
3. Boot Fire into recovery: hold volume down button & power button at the same time. If it boots to fastboot mode, use the other volume button.
4. Select Sideload
5. Connect to PC via usb cable
6. Open a command prompt with the path set to the folder where you downloaded FireOS
7. Run this command to load the firmware:
adb sideload update-kindle-global-37.5.6.0_user_560177220.bin
8. Once the recovery options come back, wipe data and cache.
9. Select reboot
