Please help connecting mybook to airport extreme

I HAVE THE WD mybook extreme I think it is 1T, if that is what comes after 1000gb!
Anyway, the mybook works just fine when connected to my macbook pro--running snow leopard. I just thought the other day, since we have another mac in the house that it would be nice to share the external hard drive. I plugged it into our airport extreme 802.11n 1st generation. I made sure file sharing was on, read and write privileges was on and gave everyone accounts. It comes up on the shared, but when I click the mybook icon it opens up and doesn't show any of the files. Can someone tell me if I am doing something wrong. Do I need a hub? Does the airport extreme not support that big of an external drive? I just can't figure out why I can't access anything on the mybook. I'm not too knowledgeable about computer terminology either so really straight forward and easy to follow directions would be greatly appreciated! Thanks so much