At the top of this page, it says ROM Downloads. In there gives you the link to the weekly and stable ROMs. And the code to look for, HM4Pro is for Redmi 4 Prime, for example. So look for the download with that in the title.
Regarding updating. If you install the weekly, then a new one comes out, you simply flash the zip of the new one without any wipes. I do wipe Dalvik after the zip though. Your settings will be saved.
After flashing the new weekly, i think you need to re flash any other zips you've been using, eg, Xposed and Superuser. But once these are done the previous settings are still there.