Follow this tutorial to Root and flash TWRP recovery on HTC DESIRE 820. Lets get started.
WHAT DO WE NEED?
– USB cable
– TWRP Recovery
NOTE- TAKE A COMPLETE BACKUP OF YOUR DEVICE. BATTERY MUST BE 85% CHARGED BEFORE STARTING THE PROCESS
STEP 1– First of all you will need to unlock the bootloader by visiting htcdev.com.
STEP 2- Enable USB Debugging. For this go to Settings -> About Phone click on build number several times to enable Developer options in your device. Open Developer Options and enable USB Debugging.
STEP 4- Power Off your device and press volume down and power key simultaneously to boot into Fast-boot mode. Now connect your
device to your Laptop/PC.
STEP 5- Now open the recovery folder and click on flash-recovery.bat. This will flash recovery on your device.
STEP 6- Now boot into recovery mode click on install zip and select Supersu.zip. Flash it.
Your HTC desire 820 is rooted now and have TWRP custom recovery. You can now flash all the custom ROM(s) to use the most out of your phone.