Arrival from Zürich airport
Take a train from the airport railway station to Zürich HB (Zürich main station). There are trains roughly every six minutes, the ride takes about ten minutes.

Arrival from Zürich main station
Take tram 3 or 14 to Stauffacher. At the crossroads in front of the tramstop walk about 250 meters to the right. The address of the Volkshaus is Stauffacherstrasse 60.

If you arrive at Zürich airport or Zürich main station and have your printed festival pass on you, you don’t need to purchase a ticket for the train or the tram!
Festival passes are valid as a personal ticket for all means of public transport including boats and the Polybahn funicular in the City of Zürich (tariff zone 10) and the airport zone (21) from 8 till 11 September (but not for the nighttime supplement payable from ca. 1.30am). See here for details on the tariff zones.