How is your setup wired? You should have CD Player to AMP to Speakers.
If the Amp has an RCA OUTPUT then you could hook the bluetooth reciever to that.
If the amp only has speaker terminals you will have to either find a bluetooth transmiter that accepts speaker terminals or use a line level converter to convert to RCA.
Now in all reality if you are just using bluetooth speakers then why are you using the amp for in the first place, its not like it is going to give your bluetooth speakers more watts of power.