To use cheat codes, you have to open your text editor and edit the "splintercelluser" and "splintercelluser1" files which you can easily find in the "\ubisoft\tom clancy's splinter cell double agent\scda-offline\system" folder. Search for the area with the key bindings. There you can bind one of the following codes to a function key. You can activate cheats by pressing those keys during the game.
Invincibility: invincible 1
Invisible to NPCs: invisible 1
Get health: health
Get ammunition: ammo
Flight mode: fly
Disable no clipping and flight modes: walk
Freeze enemies: playersonly
Kill all enemies: killpawns
No clipping mode: ghost
Airfoil round: summon echeloningredient.eringairfoilround
Flashbang: summon echeloningredient.eflashbang
Frag grenade: summon echeloningredient.efraggrenade
Smoke grenade: summon echeloningredient.esmokegrenade
Sticky camera: summon echeloningredient.estickycamera
Sticky shocker: summon echeloningredient.estickyshocker
Wallmine: summon echeloningredient.ewallmine