How can I get from the centre of Vienna, like Stephansplatz, to Gasometer?

If you come with car you need to travel on highway (Autobahn) A23 Südosttangente and take the exit towards “St. Marx”… but, since you wanted to know how to get from the center of Vienna, you can travel with the U3 towards Simmering, but make sure to leave the metro at the station Gasometer. This line stops at the Stephansplatz, making the travel very easy. If the concert at Gasometer lasts for a long time you might need to use night bus line N75 to get back to the center.