Click on the Start button in the bottom left corner of your screen
Click on the Settings icon (gear icon)
Click on Personalization
Click on Background in the left menu
Under Background, you can choose to use a picture, solid color, or a slideshow as your wallpaper. Click on the option you prefer.
If you choose Picture, click on the Browse button and select a picture from your computer. You can also use the Browse button to select multiple pictures for a slideshow.
If you choose Solid color, click on the color you want to use as your wallpaper.
If you choose Slideshow, click on the Add a folder button and select the folder containing the pictures you want to use. You can also adjust the slideshow settings such as the interval between pictures and the fit of the pictures.
Click on the Save changes button to apply your new wallpaper.
Changing Wallpaper on MacOS
Click on the Apple menu in the top left corner of your screen
Click on System Preferences
Click on Desktop & Screen Saver
In the left menu, click on the Desktop tab
Click on the + button in the bottom left corner to add a folder of pictures or individual pictures to the list of wallpaper options
Click on a picture or folder in the list to select it as your wallpaper
You can also adjust the wallpaper settings such as the time interval between pictures and the fit of the pictures by clicking on the Screen Saver tab and selecting a screen saver in the right panel