If you're running Mac OS X El Capitan 10.11 or later, you can download Mac OS X Sierra 10.12 directly from the Mac App Store:
Download to breathe new life into older hardware or access classic features like the first-ever Mac integration of Siri . Released on September 20, 2016, Sierra marked the transition from "OS X" to "macOS" and introduced game-changing tools like the Universal Clipboard and Optimized Storage . Official Download Methods
There are a few ways to download Mac OS X Sierra 10.12:
Several features characterized macOS Sierra 10.12, making it a notable upgrade from its predecessors: