Please see https://releases.xamarin.com/alpha-preview-xamarin-mac-support-on-macos-10-12-sierra for the details about this release.
Please file a quick bug report if you see any behavior that looks suspicious in this preview version (and if it isn't clear whether one of the known issues in the release notes matches the problem).
Comment in this forum thread if your question is not related to a suspicious behavior after installation but instead one of the following:
Also feel free to comment directly in this thread to contribute to the community discussion about tips and tricks for this preview product.
Thanks for trying this preview!