The mod adds the horses of the Apocalypse from the Red Dead Redemption DLC. All seven horses: Death (horse), War (horse), Plague (horse), Famine (horse), Darkness (horse), Black (horse), White (horse) and bonus Unicorn (horse). You can find horses in the wild and you need to catch and ride them. Once you have captured and tamed horses, you can buy them from the store.
Replace original models horsestandard01_hilod horsestandard04_hilod horsestandard06_hilod horsestandard07_hilod horsestandard09_hilod horsestandard11_hilod horsestandard12_hilod to modified ones, then save the RPF file.