How to install TWRP on Android using Fastboot

I used the below process to install TWRP on Mi Pad.

REQUIRED LINKS AND DOWNLOADS TO INSTALL TWRP ON ANDROID PHONE OR TABLET USING FASTBOOT:

• Unlocked bootloader on your Android. Here is a Bootloader unlock guide which may help for your device.
• ADB and Fastboot installed on your PC or MAC.
  ADB Fastboot Installation guide for Windows
  ADB Fastboot Installation guide for Linux and MAC
• TWRP image for your device.
• Enough battery backup. (More than 60% of battery charge will be good enough)
• A PC with USB driver installed for your Android.

HOW TO INSTALL TWRP RECOVERY ON ANDROID USING FASTBOOT:

1. Download the TWRP recovery image to be installed on your Android. Make sure that the TWRP recovery is meant for your Android device ONLY.
2. Enable USB Debugging under Developer Options. If you don’t know how to do this then here is How to Enable Developer Options and How to Enable USB Debugging under Developer Options.
3. Install ADB and Fastboot utility on your PC or MAC. Follow the appropriate guide to install Fastboot according to the OS that you use:
   ADB Fastboot Installation guide for Windows.
   ADB Fastboot Installation guide for Linux and MAC.
4. Go to the directory where you have downloaded the TWRP image file and then open the command console or termianl on this directory on your PC. To open a command window on Windows OS in the current directory, press shift + Right Click anywhere on Windows explorer, or some folder. Then on the menu opened, just press the “w” key on the keyboard or select “Open command window here” to open a command window.
5. Now connect your Android to the PC using a USB cable.
6. Enter the following command on the command window opened:
   adb reboot bootloader
   
   to put your Android into bootloader mode where you can flash/install the TWRP recovery.
   If your Android device asks permission such as “Allow USB debugging” then just tap on OK to proceed.
7. Run fastboot devices to see if your device has fastboot permission
   If you see an output such as
   no permissions    fastboot
   
   Run the following command
   sudo $(which fastboot) devices
   
   You should see an output similar to given below
   9EB3AD95    fastboot
   
8. Now when your Android is on the bootloader mode just execute the following command on the console:
   fastboot flash recovery twrp-3.0.x.x-xxx.img
   While executing this command make sure to replace the twrp-3.0.x.x-xxx.img with the actual file name of the TWRP that you have downloaded on your computer for your Android.
   
   If you are on ubuntu execute
   sudo $(which fastboot) flash recovery twrp-3.0.x.x-xxx.img
   While executing this command make sure to replace the twrp-3.0.x.x-xxx.img with the actual file name of the TWRP that you have downloaded on your computer for your Android.
   
   You should see an output similar to below
   sending 'recovery' (11552 KB)...
   OKAY [  0.470s]
   writing 'recovery'...
   OKAY [  0.399s]
   finished. total time: 0.869s
   
9. Now execute the following command:
   fastboot reboot
   
   For Ubuntu user
   sudo $(which fastboot) reboot
   You should see an output similar to below
   rebooting...
   
   finished. total time: 0.063s

Voila, your Android is now installed with TWRP recovery. Comment and share if it  helped you. :)

Adapted and improved from : http://www.cyanogenmods.org/forums/topic/install-twrp-recovery-android-using-fastboot/