not working? not booting? no roms? which?
if just no roms:
find the config files, usually named things like... "nameofemulator.ini" maybe not you may have to look around (or be more explicit)... these can be edited with notepad.
somewhere in there is a place that tells the program where to look for the roms... you will need to edit this path to wherever you have your roms stored on your drive.
I can't get to descriptive until you tell me which emulator, or describe what exactly isn't working about the emulator...
Peace