[Sangetsu]

Take the Narita Express or the Limousine bus to Tokyo Station. From there, you can take the Yamanote line train to Ueno Station. At Ueno, transfer to the Ginza Subway line, which goes to Asakusa Station. The exit from Asakusa Station is near the gate to the Sensoji Temple. There is a police box near the gate, as well as a crowd of rickshaw drivers. They should be able to direct you (or take you) to your hotel.

It takes one hour to get from Narita to Tokyo Station. It takes a further 20 minutes or so to get from Tokyo Station to Asakusa.

You are coming at a good time, the Sensoji is putting on festival of sorts, and they have built an old Edo period type shopping street on the temple grounds.