How to download the backdrop:

• Click on the image you want, then drag it to the folder where you want to keep it (or to your desktop)

How to change your desktop background:
Windows:

• Rightclick on an empty part of your desktop
• Choose 'Personalize'
• Click Desktop Background
• Click Browse to go to your saved picture
• Choose the folder, click OK, then choose the picture

• Choose (Apple) menu > System Preferences and click Desktop & Screen Saver
• Click Choose Folder to go to your saved picture and choose it