From the New South Entrance of JR Shinjuku Station, turn away from the Shinjuku Bus Terminal and proceed directly left. Walk down the hill for approximately 100 meters.
When you see the sign at the entrance to the Keiō Line to your left, take the stairs underground and go straight down the passage.
Go down the staircase and continue going straight. You will see the KEIO MALL entrance to your right.
Go right and enter the KEIO MALL. The second shop on the left side is the Central Honshu Information Plaza in Keio Shinjuku.