If you are arriving at Frankfurt airport, go to the Regionalbahnhof railway station and take the S8 or S9 lines towards Hanau to Mühlheim am Main. If you are arriving at the Frankfurt Hauptbahnhof central railway station, you can also take the S8 or S9 lines towards Hanau.
Exit the train at Mühlheim station and head down Carl-Zeiss-Straße (see figure). The entrance to the grounds is past the halls on the right.