Hello,
To install xiaomi.eu ROM, you need to:
1) Unlock bootloader
2) Install TWRP
3) "Format Data" in TWRP, reboot to TWRP, install xiaomi.eu ROM.
To wait until the MIUI 12 release, you can install the latest xiaomi.eu MIUI 11 ROM for your device =>
https://androidfilehost.com/?fid=8889791610682876435