Step 5: Wiring the remote
If you look at all the wires coming out of the back of the head unit, there should be 1 or 2 blue ones. These are called the remote wires. If your wires are labeled they may be labeled as:
or something similar to one of those.
If there are 2 wires, there should be one labeled Amp. If there is just one blue wire, you can use that. If you have a power antenna, you will have to splice into the blue wire for use with the amp too. What you need to do is connect the 16 - 18 gauge wire to the correct blue wire. When the stereo comes on, so will the amp.
If it is a stock stereo on a car without a power antenna and no blue wire, then run the 16 - 18 gauge wire to the fuse box, and connect it to a fuse that turns on when the accessories are on. Your amp will always be on when your car is on, but it shouldn't make noise, so its OK. If it does make noise (like from the engine), add a switch so you can turn it on or off.