To see what version of macOS your system is using, click the Apple icon in the upper-left corner of your screen, then click About This Mac.
You will see a new window open with information about your Mac computer. The first line will have the name of the macOS operating system, like macOS High Sierra.
Below the name of the operating system is the version number, like 10.13.2.
Note: If you are using macOS High Sierra version 10.13.2 or higher, you might need to do some additional steps when installing Cylance Smart Antivirus. Please read the Installing on macOS High Sierra 10.13.2 or higher for more information.