Download unzip TWRP and SP Flash tool in PC.
Copy the SuperSU.-v71zip in your phone which you will find in TWRP zip.
Run spflash tool and In the menu Option tab, go to Download, and put tick in the DA DL All with Checksum”.
choose scatter in twrp folder and then select “Download only” and click download.
Now power off the phone and connect the USB cable.
The process will start and after completion a box will appear with done written on it.
Then Boot into recovery (Power + half a second the two volume buttons).
Now you are on TWRP RECOVERY.
For Rooting:Now select install zip and then navigate to SuperSU-v2.71.zip
※Please make a backup of your device before installing or updating ROM