Just type the code on any play screen.
get gamecih
You just type it in the middle of a game. That's only if it's an in-game legal cheat (Tree of Wisdom gives them).
You would type e codes while playing the game. to get rid of the codes just type them again while playing.
There are several sites that contain codes and cheats for Plants Vs Zombies, but the only thing I have ever seen actually "cheat", like unlimited sun, etc, are all trainers. I cannot speak to trainers, they can be unstable at best and can cause the game to crash, but I have put a link below to a site that has codes and unlockable items that you may find useful.
I think you can just type in the codes while playing the game. I don't know if it works when you're on menu screens, talking to Crazy Dave, etc. I just know that it works when you're actually doing one of the levels.
you can't add cheats on plant vs zombies but you can type on the screen the normal cheats like daisies,future etc.
you type cheat codes in like this snow1
there is no cheat codes menu .
Well for starters there is the toggle code sukhbir then the mustache code type mustache also the lawn mower code type trickedout the glasses code type future the daisies code type daisies the candy code type pinata. NOTE some require tree of wisdom height
moshi cheat codes are codes u type in when you log in 2 moshi monsters
nowhere because there are no cheat codes for halo 3
type one cheat at a time