If you are asking about xiaomi.eu roms, follow the link "ROMs DOWNLOAD" just below the logo.
Then you have to choose if you want to go with the weekly or with the stable version.
Coming from a weekly, if you want to install the stable you'll have to wipe your data also.
To get the correct ROM for your device look for files containing "hermes" in the name.
There are just one version for both standard and prime.
Start installing TWRP recovery.
I don't know if something different is needed because of all the changes that happened during these last months, but I've installed it from the stock recovery.
I can't remember the exact steps because I did it just once some months ago.
Probably you just need to save the zip as "update.zip" in you internal storage and the from the recovery and run something like "update from zip".
Anyway you'll find a lot of guides about that, even on the official forum.