When you go on to the campaign page press (X) and then select the skulls that you have collected.
you have to restart the game and activate skulls from the main menu
To select the skull menu in Halo 3, go to the main menu and choose "Campaign." After selecting your desired mission, press the "Start" button to access the pause menu. From there, navigate to "Skulls" to view and toggle any available skulls for that mission. This allows you to customize gameplay with various modifiers.
No
The first skull on halo 3 is a silver skull. Silver skulls do not award any achievements.
After finding a halo 3 skull, simply pick it up as you would any other weapon.
once you get a skull in halo 3 you can co to the campain options and turn it on different skulls do different things
13
The skulls are used to activate cheat codes, such as recovering health when you punch an enemy. You activate these by pressing X at the mission selection menu.
http://www.halo3planet.com/halo-3-skull-locations/ is were I found them
You do not jump through rings to get the tilt skull in halo 3.
the fog skull takes away your radar. you find the skull on floodgate
There are not skulls in Halo 2! It's just Halo 3!