How Do I Get the Maps on Modern Warfare 2 at the Playstation Store (10 Points Best Answer)?

This is for my little brother.My little brother has been wanting to get the 5 new maps they have for modern warfare 2, and finally he has been saving up and bought the card thing (or gave it to my mom and she bought it) well i redeemed the code on the card at the playstation store and i can't find the new levels anywhere where is it ( i don't want to get the wrong one) at and how do i download it because i have never been on the playstation store or downloaded anything from it so any help. 10 points best answer to most helpful!

Suggestion:

There should be an add on section right when you get on the playstation store, then go to disc add ons and then you can go to modern warfare 2