1. From the Apple menu  in the corner of your screen, choose System Preferences.
2. Click Software Update.
3. Click Update Now or Upgrade Now:
   • Update Now installs the latest updates for the currently installed version. Learn about macOS Big Sur updates, for example.
   • Upgrade Now installs a major new version with a new name, such as macOS Big Sur. Learn about the latest macOS upgrade, or about old versions of macOS that are still available.

My Macbook Air (Late 2012) has more than enough space free, and is running Snow Leopard 10.9.5, yet when I try to install El Capitan from the app-store, I get the message 'This version of os x 10.11 cannot be installed on this computer.' I tried contacting apple support but was not eligible. This entry was posted in Troubleshooting and tagged 10.11, El Capitan, OS X, OS X 10.11 on October 1, 2015 by Topher Kessler. Post navigation ← Reasons to both install and avoid OS X 10.11 El Capitan Fix package managers not working after installing El Capitan →. This fifth release of OS X is only available as a free download for Mac users. To install it you must have a Mac that is compatible with El Capitan. This version of OS X shares compatibility with the previous version, OS X 10.10 aka Yosemite.Here are the Mac systems with which El Capitan is compatible:- iMac (Mid 2007 or newer)- MacBook Air.

If you're having difficulty finding or installing updates:

Os X Yosemite

• If Software Update says that your Mac is up to date, then macOS and all of the apps it installs are up to date, including Safari, Messages, Mail, Music, Photos, FaceTime, Calendar, and Books.
• If you want to update apps downloaded from the App Store, use the App Store to get updates.
• If you want to update your iOS device, learn how to update iPhone, iPad, or iPod touch.
• If your Mac doesn't include Software Update, use the App Store to get updates.
• If an error occurred while installing an update or upgrade, learn how to resolve installation issues.