PC Instructions
Step 1: Click on the image you want to download.
Step 2: "Right click" on the enlarged image and choose either "Set as Background" or "Set as Wallpaper".

Mac Instructions
Step 1: Click on the image you want to download.
Step 2: Click and hold on the enlarged image and select "Save image," or "Download image."
Step 3: Navigate to your desktop pictures folder, and save image.
Step 4: Go to Appearances control panel to select your new wallpaper.