hit enter on keyboard and the serial number of your device SHOULD show in minimal adb window, if it does'nt then you've not installed your Android usb drivers correctly !
[COLOR="Red"]fastboot flash recovery[/COLOR]
after this command press the SPACE KEY ON KEYBOARD AND DRAG THE "CUSTOM RECOVERY IMAGE FILE TO THE MINIMAL ADB WINDOW then hit the enter key on your keyboard and Twrp will be flashed . IMPORTANT !! After flashing the TWRP file, you should boot directly into recovery by holding VOLUME DOWN+POWER BUTTON do not allow device to boot into home screen at first boot, otherwise stock recovery will be restored !!!
6. After booting into TWRP , FLASH THE ROOT FILE IMMEDIATELY ! WARNING ! if you don't flash the root file once in twrp, you might encounter a bootloop! some users report a password prompt while in Twrp, just press "cancel" then go to twrp home screen , WIPE-FORMAT DATA, after formatting data , go back to twrp home screen -REBOOT-RECOVERY , after that flash the root file (make sure your root file is on an external sd card .