carrozzeria fx-m90v how do I reset it?

I have a subaru station wagon that has a existing stereo in it. I had toubles with my battery and replaced it to find out that my alternator was draining it...i replaced the alternator but since the battery was out of the car for a while. Now the cd player wont play and keeps making a beeping noise. I read online that my stereo needs to be reset with the chassis number of the car...how do I do that???? Pioneer carrozzeria fx-m90v