1. Open the graphic.
2. Make sure you have enough resolution in the graphic or picture to fill your screen without distorting it. (i.e.- if your monitor is 1280 pixels x 1024 pixels, your image MUST have at least that many pixels)
3. Choose your crop tool in photoshop. Set the Width & Height fields at the top of the screen to your screen resolution. (example- Width: 1280 px Height: 1024 px)
4. Drag the crop area over the graphic, size it the way you want, hit enter.
5. Save as a jpeg.
You now have an image that can be used as a wallpaper! 
