How do I get support for my iMac? Go to Keyboard shortcuts on your Mac.
How do I take a screenshot on my Mac? Press Command-Shift-3 to take a screenshot of the entire screen. Press Command-Shift-4 to take a screenshot of a selected area of the screen. To learn more, see > About This Mac to view the model information.
How can I find the documentation for my iMac? To find the iMac Essentials guide, choose Apple menu 27-inch iMac Tech Specs, or Repair a storage device in Disk Utility on Mac in the Disk Utility User Guide.
How do I reinstall macOS? Use macOS Recovery. See the Apple Support article What to do before you sell, give away, or trade in your Mac.