The vendor should have given this to you....if bought used. In case you got a from a dealer, it might not have been set or activated.
If it was not activated/set you can set it in the service menu, Beo 4: Menu, Setup, 0, 0, GO (as far as I remember).
Ralf
My Beo: Beosound 3000, Beolab 4000, Beo 4 DVD, Beolab 5000/Beomaster 5000, Beovox S45.2 with Stands, Beosystem 7000 black with Beolink 7000, Beolink 1000, F1000 (3 cubes), Beovox 5000, Beovox 3000, Attyca 1.