Here is how to access your bonus content which you'd receive for pre-ordering Red Dead Redemption 2.
Here is our guide, with screenshots taken by us for better understanding:
Nuevo Paraiso Gunslinger Outfit
The Nuevo Paraiso Gunslinger Outfit is available in the Wardrobe after completion of Chapter 1 in Story Mode.
The War Horse will be available once you have access to the Stables through Story Mode progression.
Grizzlies Outlaw Outfit
The Grizzlies Outlaw Outfit is available in the player’s wardrobe only after the completion of Chapter 1 of Story Mode.
Volcanic Pistol, Pump Action Shotgun, and Lancaster Varmint Rifle (Special/Ultimate Edition)
The pre-order bonus weapons can be picked up for free at any Gunsmith after Chapter 1 has been completed in Story Mode.
Dappled Black Thoroughbred (Special/Ultimate Edition)
The Dappled Black Thoroughbred will be available once you have access to the Stables through Story Mode progression.
Eagle Talon Talisman (Special/Ultimate Edition)
The Eagle Talon Talisman will be available at the start of Chapter 2 in Story Mode. The Eagle Talon Talisman can be equipped from the Wardrobe.
Iguana Scale Trinket (Special/Ultimate Edition)
The Iguana Scale Trinket will be available at the start of Chapter 2 in Story Mode. The Iguana Scale Trinket can be found in the player’s Satchel under the Kit tab.
Bank Robbery Mission and Gang Hideout (Special/Ultimate Edition)
The Del Lobos gang hideout is available to players to find in the world through Story Mode progression.
The Bank Robbery Mission is available as part of Story Mode progression. In-game alerts will notify you when the mission can be played. If you miss the opportunity to play this mission during the natural Story Mode progression, you can replay it through the Story option via the Pause Menu.