Hot to add bluetooth to 2005 model with 10 speaker system

[Simonsen]

Hi all, I want to add bluetooth to my 2005 z4 so i went on ebay and purchased aux, bluetooth pług which goes on the back of the head unit. But how to use it??! If I will pick cd it will play from cd same for radio and cd changer, I tried to take out cd's from changer but then I will get a message cd changer empty and no play back from BT. It's not like it has 3rd option for bluetooth. Am I missing something?