You can select which computer is connected to the keyboard, video and mouse (aka KVM) via a push button KVM switch. That buttton is located on the top right side of the electronics rack.
There is no visible indicator of which computer is connected (it’s hidden inside the rack), but you have only two options. Also, double check that the switches on the keyboard (upper right) and the mouse (bottom) and on.
The KVM controls the keyboard, the mouse, the sound bar, the 24” control monitor (the one on the cart) and the monitor’s USB hub (not the ones on the cart). Which computer displays an image on the video wall is controlled by an app, the Wall Controller, see below, that controls whether the Wall is on or off (technically idle), its brightness and which computer output to display on the Wall.