1. Click the Apple logo in the top-left corner of the screen and selecting “System Preferences.”
2. Select “System Updates” — it’s marked with a gear icon.
3. Your computer will then check if there are any updates or upgrades available for your Mac.
4. If there are upgrades available, click “Upgrade Now” to continue.
To make things easier, you can tick the box next “Automatically keep my Mac up to date” so that you won’t have to worry about making updates in the future.
If you have an older MacOS version, like High Sierra, Sierra, or El Capitan, for example, you would be able to check for updates by going to the App Store — which can also be accessed via the Apple menu in the top-left corner of the screen.