Users who have just purchased or received a Mac computer and are still getting accustomed to the macOS environment might be wondering how to change the default background to one of their choosing. There are multiple ways of achieving this task, depending on your exact needs. For example, you can set a wallpaper from the Safari Web browser directly. If you have chosen an image that you want to be your new background, right-click it and select 'Use Image as Desktop Picture' from the available options.
To use an image that is stored on your hard drive, navigate to it, right-click it, and choose 'Services.' From the available options, click 'Set Desktop Picture.'
If you wish to use one of the standard images that come with your Mac, just make a right-click on a free area on the Desktop or double-click on the Macbook touchpad. From the available options, select 'Change Desktop Background.' This should open the Desktop Preferences window. Now, just select the picture you like and it will be set as the new background. You can also reach this window by going to 'System Preferences' and opening 'Desktop & Screen Saver.' Here, you also can add your own images to the selection by adding them through the '+' sign and choosing the appropriate folder.
By picking the 'Change Picture' option and specifying the day, you can set the desktop wallpaper to change automatically.