1. Save the pictures downloaded from the Internet to the specified folder, taking the picture folder as an example.
2. Open System Preferences on the Dock taskbar.
3. Click to enter the desktop and screen saver.
4. Then select a folder picture in the left column, and the pictures under this folder will be displayed on the right.
5. If there is no folder in the left column, click the+sign in the lower left corner of the left column to select the specified folder.
6. Click on the selected picture to make wallpaper, and the desktop will be replaced (no need to confirm).