Requirements: Your MI Devices, USB Cable, Fastboot firmware, Proper USB Drivers, a windows PC.
Step 1: Download MIUI ROM Flashing Tool(MI flash tool) .
Important : Your device boot loader must be unlocked before flashing this firmware.
Step 2: Download the appropriate firmware for your devices from here
Step 3: After downloading make a new folder on any drive other than C:// drive (Important) and extract the downloaded files there. By extracting you can find a bunch of bat files and folders. If you want to flash this files via MI flash tool click here or if you want to flash it manually just download this ADB and Factboot minimal files from here and extract to the same folder and then manually flash it via executing fastboot command
Step 4:Turn off the device. Press the Volume– key and the Power button at the same time to enter Fastboot mode. Then connect the device to the Windows PC/laptop via a micro USB cable
Congratulations! you have successfully flashed the latest version firmware on your MI devices.