The Agora Museum is located inside the agora site. [Read the post on Agora: How to Get There to find your way to the agora.]

The museum sits on the east side of the agora in the restored Stoa of Attalos. If you enter the agora from the North Entrance, follow the Panathenaic Way (the main, paved walkway running through the agora) south for 50 yards. The Stoa of Attalos will be on your left and unmissable. (Coming from the Acropolis, you’ll enter the agora from the south. In that case keep walking north and the Stoa will be on your right.)

The access to the Stoa is on the southern end—the end furthest from the North Entrance. Climb up into the Stoa. The museum is located in rooms that run along the back wall of the Stoa. You can locate the entrance to the museum about 1/3 of the way down.