In order to display the PBXware interface on a projector/large screen, two things are required: a computer (preferably a laptop - for maneuverability) and a projector/large screen.
Computer and projector/large screen are connected with a video cable.
Video output on the laptop is redirected to external video output. Check the manufacturer documentation for the keyboard shortcut required for this action.
Open the PBXware interface in your preferred browser and press F11 to switch between fullscrean/normal display.