Mainz can easily be reached via Plane, Train and by car.
The closest airport is Frankfurt (FRA). From there trains brings you in half an hour to Mainz central station.
From Mainz central station Trams 51 and 53 as well as Bus 58 bring you to the university in 5 min. Schedule can be checked at https://www.rmv.de The closest stops to the venue are called "University" and "Friedrich-von-Pfeiffer Weg".
Parking on the university campus is not possible. The closed public (free) parking is called Parkplatz Dahlheimer Weg - Uni Mainz
More detailed information are found on the website of the university.