Now you can try playing your patches as you would in a performance. MainStage provides two modes, Full Screen mode and Perform mode, that optimize the display of the workspace for live performance. In Perform mode, you see the workspace and the toolbar, so you can use the toolbar buttons and access other applications. In Full Screen mode, the workspace occupies the entire screen, presenting the screen controls as large as possible for easy viewing in concert environments.
Choose View > Full Screen (or press Command-4).
Click the Full Screen button.
Choose View > Perform (or press Command-3).
Click the Perform button.
You can try both of these modes, playing the patches you added or modified, and using the controls on your MIDI controller to modify the parameters you have mapped to screen controls.