To update RevOS MIUI V12 follow these steps

1- From OTA
  1. Go to Settings, click on the RevOS logo
  2. Click on Check for Updates
  3. Read the change list and download
  4. Once downloaded you can click on Install
  5. The device will restart in recovery, install the ROM and automatically restart in the new version
2- Downloading the update from our website
  1. Download the update from our website, be sure to download the correct one and corresponding to your device (remember to check where it says "try download anyway" if you are from the mobile downloading the rom to download it from SourceForge
  2. Transfer it to your mobile device (OTG is not recommended)
  3. Restart in Recovery
  4. Flash the ROM
  5. Reboot into system