Select the dimensions matching the screen resolution of your monitor (if you don't know, select 800x600) and follow the instructions for your browser:

Macintosh Download:

Internet Explorer
  1. Select the image size under the graphic.
  2. Click/hold on the image.
  3. Select "Download Image to Disk."
  4. Save the image to your hard drive.
  5. Follow the directions under Macintosh Installation below.
 Netscape
  1. Select the image size under the graphic.
  2. Click/hold on the image.
  3. Select "Save Image As..."
  4. Save the image to your hard drive.
  5. Follow the directions under Macintosh Installation below.

Macintosh Installation:

OS X v10.x
  1. In System Preferences, select "Desktop."
  2. Under the Collection menu, select "Choose Folder..."
  3. Select the downloaded image from your hard drive.
  4. Click "Choose," and close the Desktop window.