How do you use a command-line switch??

lets see, you can type it in a dos box
or Start, Run
or add it in your shortcut (so you dont have to type it everytime)
or in a batch file (ok i'm from that time, bear with the old guy would ya)
and so on...

You could also use epsxecutor. They are entered via the command line section of the options tab for each configuration. This is the method I use.

right-click a shortcut and in the box that say 'Target' at the end of 'C:\ePSXe\Epsxe.exe' type *space*-xxx (don't put space, just put a space) and where xxx is put what prompt you want to use. You can put multiple promts as well.