It is a bit difficult to download from this site but there are several tutorials on the internet that show you how to download without having to create an account and also how to bypass the speed limit. What worked most for me was downloading a script for tampermonkey.
To flash this ROM you need to have your bootloader unlocked and a custom recovery.
Its simple to flash it just download the rom and put in a sdcard (more safe because sometimes the recovery don't show the internal memory) or the internal memory of the device.
Reboot to the recovery and perform a wipe just wipe the systen,data,cache and dalvik cache nothing more.
Be carefull and always have an backup saved before doing everything.
After the wipe, go to flash and select the location of the zip file then select it and chose confirm.
After this the rom will be istalled in your device and you can reboot to the MIUI.