Wallpapers: For PC: Click on your screen size. Right-click and choose Set as Background. For Mac: Ctrl + Click on the link and choose Download Linked File. Go into System Preferences and browse to the saved jpeg in the Desktop and Screensaver section.
Screensavers: For PC: Click Windows. Click Open. Double-click the file and click Run. Click Install. For Mac: Click Mac to download. Double-click to install.