Arriving at Bielefeld you have to leave the station and cross the station forecourt. Just straight ahead you will find the entrance to the underground tram station. You have to buy the ticket in advance at the ticket machine before you go to the platform. For an individual ticket you have to chose the options "Einzelticket, Preisstufe 1 Bielefeld". It presently costs EURO 2,50. If you are already aware of the fact that you will use public transport more often, it's worth buying a so-called "4er-Ticket" for the price of EURO 8,40, which entitles you to four trips.
From the train station, you take the tram No. 4 (direction "Lohmannshof"), which takes you to the tram station "University" within 8 minutes.