System Settings on your Mac
In System Settings, you can customize your iMac and adjust its settings to suit your needs. For example, you can add a screen saver that can also become your wallpaper, manage and share passwords, change the brightness or resolution with Display Settings, adjust Accessibility settings, and more. You can also download the latest software update.
To start, click the System Settings icon 
in the Dock, or choose Apple menu 
> System Settings, then click the setting in the sidebar that you want to adjust. To see all settings in the sidebar, you may need to scroll down.
Tip: If you’re looking to adjust a particular setting, but aren’t sure where to find it, use the search field. Results appear in the sidebar as you type.
Lock your screen. You can set your iMac to turn off the display or start a screen saver after a period of inactivity. You can also require a password in order to unlock the screen when you return to your Mac. To set up, go to Lock Screen in System Settings.
Choose a screen saver. Slow-motion screen savers can turn your iMac display into a work of art, both when you’re away from your Mac and as your wallpaper. To set up, go to Screen Saver in System Settings. If you choose a Landscape, Cityscape, Underwater, Earth, or Shuffle Aerials screen saver, you can also make it your wallpaper by turning on “Show as wallpaper.”
Remember your passwords. If you choose to store passwords on your Mac or in iCloud Keychain, you can view them in System Settings. Click Passwords in the sidebar, then enter your login information for your iMac. To see your password for a particular site, click 
, then move your pointer over the password to reveal it. You can also edit or delete as password, or click 
to share it with AirDrop.
Share passwords and passkeys with others. Set up a group of trusted contacts who can view the passwords and passkeys you want to share. If you make changes, your passwords and passkeys stay up to date. Go to System Settings, then click Passwords. Click 
, choose New Shared Group, name the group, then click Add People. After you’ve added the names of the people you want to share with, click Add. To share passwords with the group, select the group, click , choose Move Passwords to a Group, then select the accounts you want to share and click Move.
Customize Control Center and the menu bar. Choose which settings you want to appear in Control Center 
or in your menu bar. In System Settings, click Control Center in the sidebar, then choose your options.
Update macOS. In System Settings, click General, then click Software Update to see if your Mac is running the latest version of macOS software. You can specify options for automatic software updates.
iCloud and Family Sharing settings. Sign into iCloud with your Apple ID on your iMac, manage how your apps use iCloud, and set up and manage Family Sharing. For more information, see Apple ID on Mac and Use iCloud with your iMac.
Learn more. To learn more about System Settings, see Customize your Mac with System Settings in the macOS User Guide.