Open Settings menu > Modules >Remote tab.

Select the module you need (i.e., Matrix switcher, GPI output) and enable it (double-click on the [No] (to the right) to turn it into [Yes]).

Right-click somewhere on the playlist and select Add/Insert > Event > Matrix switcher.

Specify the command parameters and click OK.
An event line will appear in the playlist. AirBox will execute it upon reaching this point in the playlist.