Install a Custom Bootloader
You are well into the process now. Next, install the FIREFIREFIRE custom bootloader:
1. Take the FIREFIREFIRE Zip file and place it (still zipped) into c:\kfu\software. At this writing, the latest filename is called fff-u-boot_v1.4a.zip.
2. Copy FIREFIREFIRE into the Kindle Fire's /sdcard directory:
adb push C:\kfu\software\fff-u-boot_v1.4a.zip /sdcard/
3. On the Kindle Fire, press the Install button. Navigate to /sdcard if needed (you should already be there by default), and select fff-u-boot_v1.4a.zip.
4. Swipe to confirm. You should get a success message:
5. Back up the stock OS so you can roll back to it at any time. In the root TWRP menu, select Backup, modify the options if you like (the defaults are fine), and swipe to confirm. Backing up will take a while, which is one of the reasons why starting the process with a full battery is so important.
Flash the Ice Cream Sandwich ROM
You're almost there! Now you just need to copy the ROM and flash it. As noted at the outset, we used AOKP in our test runs, but different ROMs may have different flashing procedures. Read the documentation for the ROM of your choice.
1. Place the .zip files containing the ROM image and Google Apps into c:\kfu\software.
2. Push the ROM and Google Apps onto the device:
adb push C:\kfu\software\aokp_otter_build-38.zip /sdcard/ adb push C:\kfu\software\gapps-ics-20120429-signed.zip /sdcard/
3. In TWRP, select Wipe > Factory Reset. This will remove all existing files from the data and cache partitions, but it won't affect the /sdcard directory, which contains media files.
4. In TWRP, select Install. Navigate to the ROM .zip file that you placed on the device, tap it, and swipe to confirm. This will take a few moments:
5. Once that is done, tap the Back button in the upper right corner, and repeat the process with the Google Apps .zip file.
6. Tap Reboot System in the lower right corner, and boot into your brand-new Android 4.0 experience! If you wish, you can now remove the ROM and Google Apps .zip files from your device.
You should have a fully functioning Android tablet in your hands, so play around with it and let us know what you think. If you run into any problems during installation, share them in the comments below so that the community can pitch in and help you solve them. Good luck!