From Ryogoku Station take the West Exit which leads out into a large car park. Turn right and walk along keeping the line of shops to your right. After the shops you will see a sign marked Edo Tokyo Museum, and beneath the sign there is a big red arrow pointing to the right. Follow the path marked by arrows and you will swiftly arrive at the museum.
From Shinjuku Station to Ryogoku Station:
Take the Chuo-Sobu Line direct to Ryogoku Station (22 minutes, ¥220)
From Tokyo Station to Ryogoku Station:
Take the Keihintohoku Line to Akihabara Station, change to the Chuo-Sobu Line to Ryogoku Station (11 minutes, ¥160)