Follow the instructions on how to flash the device carefully from the link above
I will not take responsibility on whatever may happen to your device.
Make sure you are downloading the exact ROM of the device you want to flash because
flashing a wrong preloader, will make the device completely dead
(can’t power on, can’t charge and will not be detected by a computer)
Flash this ROM using Miracle Box
Learn how to flash MTK Android devices Using Miracle Box from here