By default, the main window, opens up on the primary display (monitor). If you are using multiple or dual monitor setup then you can choose to display it on second monitor.
From Tools menu, select switch monitor command and choose the monitor you wish to display the clock window on. The settings will be remembered when you start the program next time.
The floating desktop (analog & digital) clocks has no effect with the switch monitor command. You can move the desktop clocks to any position on any monitor. The position will be saved and the clocks will be placed at the same position when you start the software next time.
The world clock wallpaper is displayed on all the monitors. Currently there is no option to display it on any one monitor.