Hello,
when using several monitors, arrange how you will see applications when moving them from one display to another. For this, in the Mac OS X menu select: System Preferences -> Displays -> Arrangement. Arrange the displays in the Displays dialog using drag-and-drop operation.
But if you want to use Dual monitor when in Coherence mode, please open 'Configuration Editor' of your VM (Edit -> Virtual Machine) -> 'Coherence' tab and enable 'Use multiple displays'.
Best regards,
Stacey