speedball

I have a '09 edge with factory dvd in rear headrest. The remote will not work and yes the batteries are good. Is there a way to program the remote to the headrest? Lets assume that you buy a remote online and receive it in the mail. You open the box, install the batteries and then what? How do you link it to the dvd system. I have searched for a manual online but no luck. PLEASE HELP this is driving me insane! Thanks