On a PC: Right-click the avatars (for Facebook, Twitter, etc.) you want to download, and then click Save Picture As... .Choose the location to which you would like to save the image and click Save.
On a Mac: To download the avatars (for Facebook, Twitter, etc.) you want, click and drag the image to the desktop or a document in another application. You can also Ctrl-click the image and select either Save Image As... or Copy Image to Clipboard.