To change the desktop background
Open Desktop Background by clicking the Start button and clicking Control Panel. In the search box, type desktop background, and then click Change desktop background.
Click the picture or color that you want to use for your desktop background.
If the picture you want to use isn't in the list of desktop background pictures, click an item in the Picture location list to see other categories, or click Browse to search for the picture on your computer. When you find the picture that you want, double-click it. It will become your desktop background. If you would like to set your background as a solid color, just click on Solid Color from the drop down menu.
Under Picture position, click the arrow and choose whether to crop the picture to fill the screen, fit the picture to the screen, stretch the picture to fit the screen, tile the picture, or center the picture on the screen, and then click Save changes.