From the Western Train Station (Westbahnhof):
Underground line U3 to Volkstheater, then U2 to Schottentor/Universität. Then walk 2 minutes , or take tram lines 37, 38 or 40 and get off at the first stop.
From the Southern Train Station (Südbahnhof):
Tram line D (direction Nußdorf) to Schottentor/Universität. Then walk 2 minutes , or take tram lines 37, 38 or 40 and get off at the first stop.
From the airport:
S7 railway line to Landstraße/Wien-Mitte, change to U4 and go to Schottenring. Then take the U2 and go 1 stop to Schottentor/Universität.