Your device must be detected by your system to use this script (drivers installed on windows, udev configured on Linux

1) Reboot your device in fastboot mode : shutdown it, then power on it again by pressing CALL+POWER and wait for fastboot menu
2) Launch 1-LINUX-Recovery.sh if you running linux, or 1-WINDOWS-Recovery.bat if you running windows, the device will reboot.
3) Reboot your device in mini-recovery mode : shutdown it, then power on it again by pressing VOL DOWN + CALL + POWER.
4) When in mini-recovery, run 2-LINUX-Tools.sh if you running linux, or 2-WINDOWS-Tools.bat if you running windows, the device will reboot automatically in recovery.
5) Choose "root this device"
6) Choose "reboot"

Enjoy.