It is very important to keep your MacBook's operating system current with updates. When you see that an update is available in your notifications, you should be sure to run the update at home when your device is plugged in. If you're not sure if you need an update, follow these directions.
If your system requires an update this must be done at home with your computer plugged into the charger.
Plug your computer into the charger in a safe location with internet access. It is best to run operating system updates while at home.
Click on the Apple in the top left corner of your screen and select “System Preferences”.
Locate the “Gear” Icon “Software Update” and open it.
Underneath “Other updates are available” select “More info" (Do NOT click Upgrade Now).
The available updates should be listed and checked. Press “Install Now” and follow the prompts.
6. Updating may take some time, and your computer may restart several times during the process.