In Desktop & Screen Saver preferences, you can change the picture thatโs displayed on your desktop. Here is how:
Choose Apple menu > System Preferences, click Desktop & Screen Saver, then click Desktop. Now, to find the picture you want to use, click "+", navigate to and select the folder, then click Choose.
All your pictures in the folder will load on the right side. Click the picture you want to use as wallpaper and you are done.