How do I use the new maps and the zombie map on black ops?

I just downloaded the new map packs for black ops but how do I use the new multiplayer maps?? and I tried using the zombie map ascension but won't let me use it.. i havent completed the campaign yet nor tried the zombie map kino der toten, if that helps.. ThanksHow do I use the new maps and the zombie map on black ops?
first of all bro you have to beat kino der toten before you can move on to ascension man on the multiplayer maps i dont know it just let me use them.