I've downloaded the Legendary Map Pack off the xbox marketplace but how do I play it

[FishBoy]

on my copy of Halo 3? It shows that it is on my hard drive but doesn't appear when I want to play them in custom games they do not appear!
The same thing has happend when I downloaded the Heroic Map Pack

 

[idk]

That happened to me before just try signing out and then signing in on another account or rebooting your 360

 

[dØØFiS]

you need to be online to play the map pack