There are two mains outs on the rear. one for the amp, one for a tuner. Plug the amp into the preamp if you want the amp off when not in use. You can also plug it into an outlet strip or power conditioner that has a switch.
It is not a bad thing to leave the amp on 24/7 as it might sound better after being on for a while.
If you don't have the owners manuals you can download them free from www.hifiengine.com