Dual monitors

I am running FCPX on an iMac 27" and have another monitors that I would like to use for jus the thumbnails of the captured footage. When I hook up the second monitor using the HDV cable I get a mirror image of the iMac 27. How do I setup the second monitor in order to just show the captured footage thumbnail images?
Thanks in advance for your response.

You can easily switch between mirroring or "extended desktop" just ny pressing Command-F1.

Then in FCP X the option to click Window->Show Events on Second Display becomes active.

Edit: in case it happens that your second display shows up on the wrong side (say it is physically on the left of the iMac but it appears as if it is on the right), then go to System Preferences->Displays->Arrangement and drag its representation so as to mimic the real location.