Timmy Griffin

I recently installed a double din gps dvd player radio in my 03 trailblazer I originally installed an add a fuse and attached my 12 volt wire from the radios wire harness to the fuse box under the hood. The problem with setting it up that way was the radio would only turn on when the car was running and as soon as I shut off the car the radio would not be useable. I re routed that 12v wire to the fuse box I the back under the driver side rear seat to aux console 1 slot wich allowed me to power the radio on without having to insert a key in the ignition. Problem with that is after one day wired that way my battery was completely dead. I want to know how can I set my radio up so that my radio can power on with one click forward of the key like the factory radio did instead of two clicks forward where the dash lights come on and the fuel pump primes. also want it so when I shut the car off the radio stays on until i open the car doors. So i need help finding where to wire this 12v so I can do such. Can anyone lead me in the right direction? Tia!