I didn't, but there is (at least) one line going to your stereo (off the top of my head I want to say it's blue, but I'm not sure) that has 12v power when the ignition is switched on. If you have a multimeter, you can switch it to volts, hold the black probe to a ground and stick the other probe in the harness till you find a wire that's 12v. Or if you can find the manual for your stereo or harness it might say.. or there might even be a tag on the right one.