Open the Settings Menu then press Triangle to open the Cheats List then Triangle again to enter the password. For some cheats, you'll need to meet a requirement in-game before you can use it, which will be listed below. Please note that using Cheats will disable Trophies.

Effect	Password
Create Buggy	Keep your dreams light.
Create Circus Wagon	Would you be happier as a clown?
Create Race Horse	Run! Run! Run!
Create Superior Horse	You want more than you have.
Create Wagon	Keep your dreams simple.
Create War Horse (Requires a newspaper)	You are a beast built for war.
Decrease Wanted Level	You want freedom.
Drunk	A fool on command.
Fog of War: Reveals entire map	You Long for Sight but See Nothing.
Fortify Health, Stamina and Dead Eye Bars (Requires a newspaper)	You Seek More Than The World Offers.
Heavy Weapons: Pump-Action Shotgun, Bolt Action Rifle, Mauser Pistol, and Semi-Automatic Pistol (Requires a newspaper)	Greed is American Virtue.
High Honor (Requires a newspaper)	Virtue Unearned is not virtue.
Increase Wanted Level	You want punishment.
Increase Whistle Range For Horse	Better than my dog.
Infinite Ammo (Requires a newspaper)	Abundance is the dullest desire.
Infinite Stamina (Requires a newspaper)	The lucky be strong evermore.
Own All Outfits (Requires a newspaper)	Vanity. All is vanity.
Reset Honor	Balance. All is balance.
Set Dead Eye Level 3	I shall be better.
Set Dead Eye Level 5	I seek and I find.
Set Health, Stamina, and Dead Eye Bars to Full	You flourish before you die.
Simple Weapons	A simple life, a beautiful death.
Stealth Weapons	Death is silence.