To determine your screen's resolution go to the control panel and check in the display settings for your monitor's resolution or for an even simpler solution just visit the website
http://www.whatismyscreenresolution.com/Choose the Wallpaper that comes closest to your screen resolution. Remember though it doesn't have to be exact. When applying the photo to your desktop simply choose the option to "stretch" the photo to make it fit your screen.
Ordering Instructions: Once you have determined your screen resolution go to the gallery that best fits your resolution and begin deciding which 10 wallpapers you would like to purchase. Once you have an idea of what you want go to the “Buy” menu and select “select products.” Choose “Wallpaper package 10 for $10.” (Leave the quantity at 1 unless you want to purchase more than one bundle of 10 photos.) Then click on the continue button in the bottom right hand corner. Select “more” to see all the wallpapers and begin dragging them into the place holders. Once you have filled up all the spaces select “add to cart” and proceed to the check out.