The code below will insert between the "head" tags of your html document, the main thing you should know about this code is that you need an image that is at least the width of the page you are trying to cover. Most screen resolutions are 800X600 or greater. When you preview your pictures in your "Pictures" folder, you should be able to mouse over individual pictures to see exactly how big they are (i.e.500X786, etc.).
If you have any questions leave them in the comments area of my blog.