How do you get cd changer to work where none was fitted to car originally?

Hi guys, I have just bought and fitted a radio/cd player (Pug original) to my 02 plate 307 1.4HDI as it had an aftermarket stereo in. The remote on the column obviously wasn't working with it so I wanted an original equipment one. It was ordered from Performance Peugeot in Cheadle, Stoke on Trent, I paid an extra tenner and they programmed it to work with my vin number.
I then got a nice 5 disc cd changer but cannot get it to even power up. I have tried 2 and same result not powering, even having spent £8.99 on both of them for the code,any ideas, A/ on how to get it to power up and B/how to input the 4 digit code in, thanks.