I plug it into the USB port but it's like not working, it doesn't show that it's responding.

You probably need to download the latest microsoft controller software so it reads the controller. Then go into Frets on Fire and set the Keys. If you're on a Mac then I don't know what to tell you.

Where can I get it?

EDIT: Lol, my friend sent me the program to maxe the X-plorer controller work for the Mac.