Networking external HD

I have been trying to connect my external HD to my router so I can network my movies and watch them on all the devices in my home.  I have a WD external HD that I am storing my files on. when I pug the HD into the USP port it will not recognize that anything was plugged in. I then plugged in a thumb drive that had a few videos on it and that worked fine. what do I need to do to my WD external HD to get my router to recognize that it is plugged in? the plug itself does work and power was going to the External HD when I plugged it into the router.