You can find in this page direct download links to MIUI 8 v6.6.1 Fastboot and Recovery ROMs Alpha Build v6.6.1 for Mi 5, Mi Max, Mi Note, Mi 4, Mi 3, Mi 2, and Mi 2S. Installing Alpha ROM could be a great idea for those who want to taste the awesomeness of MIUI8 before everyone else. However, if flashing custom ROM is something you believe it too advanced for you, then installing MIUI 8 theme may be the best alternative.
Users might have difficulties at the beginning operating MIUI8 China ROM features. Moreover, no Google Apps like Play Store, Google Calendar, and so on, are available. However, for those getting MIUI 8 based on Android 6.0 Android Marshmallow can simply install it using this Gapps package.
Luckily, there’s a nice video demo by Xtreme Droid showing how to install this Alpha build of MIUI 8: