Select ‘ System Preferences ’ from the drop-down menu.
In the ‘ System Preferences ’ window select ‘ General ’.
Under ‘ Appearance ’ select ‘ Dark ’.
The Apple menu bar and dock will immediately darken, as will the backgrounds and menus of any applications that support dark mode.
When you activate ‘ Dark Mode ’ you may wish to change the ‘ Accent Colour ’ used throughout the user interface for menus, buttons, form fields and more. To do so, select from the colour options shown next to ‘ Accent colour’ .
Changing the ‘ Accent colour ’ will also change the ‘ Highlight colour ’ (the colour used to highlight text when you select it) to match. If you wish, you can select a different colour to use just for highlights - click on the drop-down menu for ‘ Highlight colour ’ and choose from the options.
When you are happy with your settings, click the ‘ Close ’ (red) button at the top of the window or press ‘ Cmd ’ + ‘ W ’ to close the window.
Note : If this does not work it could be because your computer settings are managed by someone else (an IT department or administrator for example) in which case you will need to contact them to access these settings or for further help.