[TIP: As it's been said before, you can start exploring the Soul Arbiter's Maze at once - it's not mandatory to collect all Soul Arbiter's Scrolls.]
Naturally, begin by planning the journey to the [Soul Arbiter's Maze] (the above screen) from the world map; it's located in the east of the Kingdom of the Dead, in the area which neighbors with the Spine and the City of the Dead. Enter the dungeon when you're there.
Destroy the objects lying around to get a Boatman Coin, then start going up where shown on the screen, climbing the pegs as they go.
After grabbing onto the last one, wall-run up the wall and then bounce off it. You need to catch an interactive handhold in flight, using of course Death Grip. Repeat the same with the other handholds. When you land on a small ledge, flip the switch.
Jump down and head for the newly unlocked interactive pegs located on the west wall (the above screen). Same as before, bounce off the wall when you get to the top, the latch onto grapples with Death Grip. When you're on the new balcony, look inside the nearby chest.
Take the door on the opposite end of the ledge you're presently on (the above screen). Go through the linear hallway to officially reach the [Soul Arbiter's Maze].