To move the Dock and menu bar to an external display on Mac OS X, you can follow these steps:
Connect the external display to your Mac using an appropriate cable.
Open the System Preferences application and go to the Displays pane.
In the Arrangement tab, click and drag the white menu bar at the top of the display layout to the external display. This will move the Dock and menu bar to the external display.
Close the System Preferences window.
After completing these steps, the Dock and menu bar will be displayed on the external display, and you can use the Mac as usual. This can be useful when using multiple displays, as it allows you to keep the Dock and menu bar on a separate display from the main desktop.