OS X Yosemite: Keep your Mac up to date
Periodically, Apple releases updates to your computer’s software (which can include important security updates).
If you receive a Software Update notification, you can choose when to update your software, or choose to be reminded the next day, right in the notification.
You can also check the App Store in the Apple menu to see if there are any updates.
Check for updates manually
To get your updates, choose Apple menu > App Store, then click Updates.
Set your Mac to check for updates automatically
Choose Apple menu > System Preferences, then click App Store.
Select “Automatically check for updates.”
To have your Mac download updates without asking, select “Download newly available updates in the background.”
To have your Mac install app updates automatically, select “Install app updates.”
To have your Mac install OS X updates automatically, select “Install OS X updates.”
To have your Mac install system files and security updates automatically, select “Install system data files and security updates.”