Please see https://releases.xamarin.com/beta-release-cycle-9-refresh-builds/ for the details about this release, including the steps to update or downgrade as needed.
This version contains a number of known issues that are under investigation. Additional bug reports are welcome!
Please file a quick bug report using the "Cycle 9 Preview" new bug form if you see any suspicious behavior in these versions that you wish to report.
Comment in this forum thread if your question is not related to a suspicious behavior after installation, but instead one of the following:
You notice an error in the Release Blog post.
You have trouble downloading one of the installer packages.
EDIT Jan 18: Update link to Release Blog post for new versions.