Steps to upgrade the Mac OS Catalina OS X 10.15:
- Select Software Update from the System Preferences menu. Alternatively, use the App Store app and search for macOS Catalina under the Featured tab (+ 1) or on Apple's Catalina download page.
- To begin downloading the Catalina installer, click the Upgrade Now or Download option.
- The installer will start on its own and launch automatically after you download macOS 10.15 Catalina. To complete the upgrade and begin using macOS Catalina, follow the on-screen instructions. Select either the internal hard disc or an external hard drive to create an external macOS drive when requested.