If you mean to use the trackball/spinner to control MAMEWAH - you can't...
If you mean when playing MAME then you need to setup MAME (not MAMEWAH):
Create an ini file, by doing 'mame -cc' at a command prompt. Then edit mame.ini (assuming your mame exe is 'mame.exe'). Then make sure it has 'mouse 1' in it.
That should do it
