command line = dos prompt
you basically run it from a dos window with that switch, or you make a shortcut to the pSXEmu exe and put the switch at the end of the link in the shortcut.
i wouldnt guarentee that fixing your problem tho, some other games (like final fantasy 7) have issues with screwy sound. Remember this is the 1st (and second) release of the emu, dont expect perfection