find either a power wire in your fuse box that is on when the accesories turn on, or you can look for the power antenna on your head unit if it has one. And yes, your amp needs the remote to turn on, its what tells it to turn on or off. If you can't find either, you can run a wire to the battery, and to a switch, and from the other post on the switch to your amp. If you use a swicth though, you'll always have power to your amp whether the cars on or off so you'll have to make sure your switch is off when the car is off.
you could just connect the remote wire to your speakers in the front or back. as long as they are off when the ignition is switched off. thats what i am going to do on mine because i dont have a remote power wire in my head unit.