If it has the premium audio system with the factory amplifier you should have a wiring harness that has RCA inputs on it that will attach to the pre out on the head unit this is the feed the factory amplifier that intern feeds the speakers you can't wire from straight head unit to the speakers without bypassing the amplifier
http://www.autoradioforum.com/showt...da-Civic-EX-with-premium-sound-(external-amp)
You would have to either find an adapter that will brodge the amps wiring harnesses together or sploce them manually. I don't recommend bypassing the amp though unless you change all the speakers. In which case your better served running new speaker wire instead of using the factory wiring.