Select the dimensions matching the screen resolution of your monitor (if you don't know, select 1024x768) and follow the instructions below:
- Select the image size under the graphic.
- Click/hold on the image.
- Select "Save Image As..."
- Save the image to your hard drive.
- Follow the directions under OSX Installation below.
- In System Preferences, select "Desktop."
- Under the Collection menu, select "Choose Folder..."
- Select the downloaded image from your hard drive.
- Click "Choose," and close the Desktop window.