How To: Use cheats in GTA IV

what cheat of gta, me i help me what cheat of gta\

i dont know how to use the phone. like the one half of the phone is under the screen. and i dont know how to use it :P ???

how are you supposed to enter those long numbers to make the wanted level go down while you're being chased like crazy?

how do u even get te cheat code entering up, sorry I don't have a clue !!
plz help ive got loads of codes but don't know where to type them in to !