Overview
Apple releases bug fixes, vulnerability patches, feature improvements and even OS upgrades for macOS and its apps via Software Update. Although your Mac automatically checks for new updates once a week, prompting you if there are new updates available, you can manually check to see if there are any available macOS updates or upgrades.
Instructions
See Also
Keep your Mac up to date
How to upgrade macOS
Software Update Management on University Macs
Troubleshoot OS Updates on macOS (Faculty/Staff)