How do I get the map packs of call of duty 5 Nazi zombies?!?

I really can't find the Nazi zombies map pack (ps3) on the playstation store. I search for it but something else keeps on coming. I updated the disk so I thought maybe it would help. But I didn't. Can someone please tell me a step by step guide on how to get it? (plz ppl) don't answer dum questions! :p