FCP-X using dual monitors

I need guidance regarding using a second monitor for viewing program play-back while editing on FCP-X. I have an HDMI cable going from my iMac 27 to the HDMI input on a Samsung monitor but can only achieve a mirror image of my iMac screen.

A step by step guide would be most appreciated.

Thank you.

I don't have an answer but you could try asking over at the COW:

Also on Facebook there are a few good FCPX user groups.

If you find an answer please post your findings back here.