Like the previous build, macOS Sierra 10.12.1 beta 3 doesn’t include any major user facing changes, however bug fixes, stability improvements, and security enhancements are here. The release notes for this build don’t say anything exciting, so we’re gonna have to assume all changes were made under the hood.
To install macOS Sierra 10.12.1 beta 3 on your registered Mac, head over to the “Updates” tab in the App Store and check for updates. There, you’ll find the new build ready to install. Just click the “Update” next to the macOS Sierra 10.12.1 Beta 3 listing and restart your Mac. The process may take a little while, so be patient and don’t turn off your Mac manually if you don’t have to.