Back up device won't unmount
I purchased (from Apple) a recommended external hard drive device for backing up my new desktop iMac (10.7.3).
It is a Porsche Design Mobile Drive P'9221. I went through the set-up instructions, however I notice it has a folder on the desktop, not the image of the drive. Anyway, maybe I have not set it up correctly, but I cannot get it to un-mount. I drag the folder icon to the trash and when I try to disconnect, I get a warning saying I have done it incorrectly and may lose information.
What should I do?
iMac, Mac OS X (10.7.3)