Go up the stairwell and once you arrive at the first landing, where the fountain is, enter the loggia and take your left. You will find a door there leading to the ticket office, which, once you cross it, will be to your right. After getting your ticket, you can make the path back to the first landing of the stairwell. While inside the loggia, you will find stanchions telling you what direction to take. As you stand with your back to the door you just crossed, continue straight ahead towards the staffer that should take your ticket. Then, go through the door past him and take the spiral staircase up to the very top. The stairs will open to a hallway. You will find a fountain with water running on the wall before you go. Go stand in front of it to learn about this hall.