Using public transports
From Hauptbahnhof Hannover walk to the subway station Kröpcke (about 500m from the main entrance of the railway).
Take the subway No. 4 (direction Garbsen) to the station Schönebecker Allee.
From there a shuttle bus (No. 404) is driving to the campus Garbsen.
You will find electronic time-table informations here