While "Options" is highlighted at the main menu, hold L1 + L2 + R1 + R2 to 
display the "Security Clearance" screen, with a password entry prompt for 
the "Invulnerable", "Infinite ammo", "All missions", and "All bonuses" 
options. Hold X and press D-pad Left or Right to change one of the 
characters in the desired password. Release X to input that character. 
Press Right to highlight the next character and repeat until the password 
is filled. Press Square to accept the password. If you entered the code 
correctly, the text will turn orange. Press Triangle to exit the password 
entry screen.