Step 1: Download and extract the stock firmware on your computer.
Step 2: After extracting you will find the SP Flash Tool, Driver and instruction manual.
Step 3: Install the USB Drivers (skip if drivers are already installed).
Step 4: Open the SP Flash Tool and load the Scatter File from the firmware folder.
Step 5: Connect your Smartphone to the computer using the USB Driver.
Step 6: Click on Upgrade / Download Button in the SP Flash Tool to Begin the Flashing.
Step 7: Green Ring will appear at the end of successful Flash.
Important Notes:[*] Take a Backup of your personal data before flashing or installing the firmware on your smartphone. As this helps you to recover the personal data whenever any thing wrong happens.