Simple steps to download and install the latest version of macOS (formerly known as OS X).
Apple has made it easy to download and install macOS Sierra, even if you are running an older operating system. If your Mac is running Lion (OS X 10.7.5), Mavericks, Yosemite, or El Capitan, here's how to download macOS Sierra:
Click on the Apple icon in the upper left corner of your screen.
Click on App Store....
Click on Featured.
Click on macOS Sierra in the Mac App Store.
Click on Download under the Sierra icon.
Wait for macOS Sierra to finish downloading.
Click Install to begin the installation process.
If you can't find macOS Sierra under the featured section of the Mac App Store, try searching for "sierra" or going directly to the macOS Sierra download page.