Change the desktop background
To change the image used for your backgrounds:
Open the Activities overview and start typing Background.
Click Background to open the panel. The currently selected wallpaper is shown at the top.
There are two ways to change the image used for your backgrounds:
Click one of the background images which are shipped with the system.
Some wallpapers change throughout the day. These wallpapers have a small clock icon in the bottom-right corner.
Click Add Picture… to use one of your own photos. By default, the Pictures folder will be opened, since most photo management applications store photos there.
The settings are applied immediately.
For another way to set one of your own photos as the background, right-click on the image file in Files and select Set as Wallpaper, or open the image file in Image Viewer, click the menu button in the titlebar and select Set as Wallpaper.
to view your entire desktop.