how do you turn skulls on for halo 3?

[Rellik]

i know where most of the skulls are but when i get to them i cant pick them up (im playing co-op) help me!

 

[VicSkimmer11]

If your playing coop you should still get the skulls. Note that only the gold skulls give you achievement points. The silver ones do not. To turn on the effect, when your in the campaign lobby hit the "X" button and it will bring up all of the skulls and the scoring system.