Extract SP Flash Tool and launch.
Now click scatter-loading button so that flash process can begin.
locate the scatter file of the device. It will be inside the folder of the rom you downloaded.
Untick Preloader (not really necessary but a great precaution) tick this if the device is completely DEAD.
Please make sure you untick DSP_BL if found on the list shown in SP Flash Tools especially when trying to flash devices with older chips like mt6572, mt6577 etc
Now click download button.
Power off the device and remove battery (if battery is built in don’t worry just continue ).
Most new devices now require battery for flashing.
Connect the device to the computer with USB and wait for SP Flash Tool to detect it.
Hold volume down or volume up button and connect the device for easy detection.
Once phone is detected a red line will be seen at the bottom followed by a yellow line.
When flashing is completed, a green tick is shown on the screen. Older versions of so flash tool will show a green circle.
Insert battery back into the phone and reboot device