In transformers the game how do you get to the diffuculty screen to enter cheat codes?

It is for the ps2 and can someone please help me.In transformers the game how do you get to the diffuculty screen to enter cheat codes?u dont enter them in the difficulty screen you enter your cheat codes at the main menu where campaign, bonus, etc... can be seenIn transformers the game how do you get to the diffuculty screen to enter cheat codes?Try to finish it without cheats... my mate bought that game (from bali) when it wasn't even bought out yet... and he finished it without any cheats.