Under Fire

How do I get to the cheat mode in 007 agent under fire for ps2?

Every time I put a cheat code in it doesn’t work I do it exactly the way it says. Oh and no funny guys out there answer this spare me the time of reading you shouldn’t be cheating because first of all I could care less and second of all I already finished the whole game. I want to play it with unlimited life, guns, and ammunition thanks.
I don’t know where to enter the codes in or even if the I am sticking it in the right place. When I stick the code in the level because it says hit start it will usually have an x in it and that means it will unpause the game. Is there a certain thing that I have to hit to enter it in?

http://www.gamewinners.com/playstation2/JamesBond007AgentUnderFire.htm

Soldiers under fire in Bahgdad, Iraq