Blender dual screen - how do you do it?

Just wondering if anyone can tell me how to run Blender on two monitors - I can’t figure out how to seperate a screen from the rest to move it to the other monitor. Any ideas?

I’m using OS X if it matters.

Cheers

most people define the Blender window to be W-I-I-I-I-I-D-E, spanning both monitors. and tell your graphics card to span the single display to both monitors.