The automatic backup feature only works if you have WD Smartware or any other backup software with that feature installed on your computer.
After installing WD Smartware you will have to go to the backup tab and click on Run or Start backup (first time only). Then everytime you have new media files on your computer (music, videos, docs, pics) those files will be copied automaticly to the passport drive.
If the drive is unplugged when you are saving or downloading new media files on the computer, when you plug the drive again that data will be copied automaticly.
WD Smartware is a software that always run on the background of your computer that means run the first backup manually like I mentioned before and forget about the rest, keep using your pc as ussual.-