If you've flashed a ROM before, it's exactly the same. Unlock the device, flash TWRP, install ROM. Exceptions:
- Make sure to securely backup EFS using the TWRP backup function and persist.img using
adb shell dd if=/dev/block/bootdevice/by-name/persist of=/sdcard/persist.img
while you are still in TWRP. - Unlocking your device requires a Mi Account. You can find instructions on how to do this in developer settings.
- You may get stuck in recovery until you format data when you try to boot into your ROM after flashing.
- Read the full instructions to know when to wipe