Apple today released a second beta of an upcoming iOS 10.1 software update and a third beta of an upcoming macOS Sierra 10.12.1 software update to non-developers who are enrolled in the official Apple Beta Software Program.
Both macOS Sierra and iOS 10.1 public betas can be downloaded over-the-air through Apple's Software Update mechanism on devices enrolled in the beta program. iOS devices must have the proper certificate installed to run public betas.