pres as and keep it pressed i think, then switch it on while holding the as button untill u hear a beep.
Then with the number keys type in code and then keep as pressed again till it says beep again.
Since this is ccr600 u need 2 codes, 1 for the radio and 1 for the cd changer.
this is just what i remember out of head lol... i'll take a look into my ccr600 manual later to give u exactly what u need to do if some1 else doesnt beat me to it lol