Select the MacOS you are using:

Pre-MacOS Sierra (Mountain Lion, Mavericks, Yosemite, El Capitan)  >> Click here
MacOS Sierra (released 09/2016) and High Sierra  >> Click here

How to check your MacOS version?

  1. Click on the Apple icon in the top left corner of your screen.
  2. Click on “About this Mac“.

You will see a popup with your OS and its version.