Story to Unlock Horse Fast in Elden Ring
You have to use the lever to lower the elevator.
Rest at Grace: The first Step.
Rest at Grace: Church of Elleh.
Rest at Gace: Gatefront.
After that, you will need to meet Melina.
And get Spetral Steed Whistle.
You need to get hints on how to use it.
And assign the whistle to the Pounch.
Hold Triangle+right Button to ride Horse.
And click the left analog stick (L3) to dismount.