*First time user* Need startup-help with my Kawai MP9000

Have you opened Audio MIDI Setup? It's in Applications>Utilities. Is your USB to MIDI cable displayed in the MIDI Studio window? If not, try unplugging it and replugging it to get it recognized. Most USB to MIDI cables have "In" and "Out" embossed on the MIDI connectors. Usually the "In" means in to the computer, so plug this one to the MIDI out port on your MP9000. The "Out" means out from the computer, so you can plug this one into the MIDI in of your MP. You can add devices and name them for easy identification when you get into MainStage. Notice the sequence of photos where I clicked add device, then named it by double-clicking on it and entering the name in the appropriate box. I also named my USB to MIDI cable MP9000 and "dragged" MIDi cables to and from the devices.

Of course, in MainStage layout, you could have just selected "all" and you might have gotten it to work, but if you plan to use more than one MIDI device, it's easy to identify your keyboards. Now, in layout mode, select the keyboard, select "assign" in the screen control inspector(it will turn red) and play the keyboard. You can also select it manually. No sounds are produced from MainStage in layout mode, so return to edit or performance mode.