Multiple Monitor Issues

I was wondering why I couldn't click directly into my other window with two monitors in After Effects to grab my artwork. I have my timeline and controls on one window and my artwork on the other. I would have to click the window, click again to activate, then click a third time to grab my artwork. It turns out I needed to go to prefferences, enable Mercury transmission and check Adobe DV for both monitors. Not sure what all that jazz means but it worked.