Switch to Fastboot Mode
It's still not too late to turn back. Up until this point, you haven't done anything to the Kindle itself. But now you're about to take the first step that involves making changes to the tablet. So, without further ado:
1. Make sure that the Kindle Fire is still connected to your computer.
2. Create a new subfolder, c:\kfu\software.
3. Unzip fbmode.zip into c:\kfu\software. It contains a single file, called fbmode (with no suffix).
4. Open a command prompt window, and copy fbmode into a user-writable location on the Kindle Fire using ADB:
adb push C:\kfu\software\fbmode /data/local/tmp/
5. Edit fbmode's permissions so that it can run:
adb shell chmod 755 /data/local/tmp/fbmode
6. Run fbmode to switch to fastboot mode:
adb shell /data/local/tmp/fbmode
7. Using ADB, reboot the Kindle Fire:
At the end of this process, your command prompt window should look like this:
Your Device Manager should look like this:
The meaning of this notation is that the name of the device changes from Android Composite ADB Interface to Android ADB Interface.
Finally, the Kindle Fire itself should look like this:
The Fire will simply display a logo and stay put. It's not "stuck"; rather, it's in fastboot mode, awaiting further instructions.
Install a Recovery Image
Next, you'll install a recovery image--a miniature operating system that you'll use later to flash the complete ROM. The recovery image will also come in handy for creating full backups of the device, among other things.
1. Copy the TWRP .img file into c:\kfu\software. At this writing, the latest TWRP image is named openrecovery-twrp-blaze-2.1.1.img.
2. Open a command prompt window at c:\kfu\tools and install the image:
fastboot -i 0x1949 flash recovery C:\kfu\software\openrecovery-twrp-blaze-2.1.1.img
3. Change the boot mode to Recovery:
fastboot -i 0x1949 oem idme bootmode 5001
4. Reboot into TWRP:
fastboot -i 0x1949 reboot
At this point, your command prompt should look like this:
And your Kindle Fire should look like this: