To check all bus and train connections, you can use the schedule on this website: http://www.rmv.de/en/. You can also download the RMV public transport application on your phone. Alternatively, you can also check out https://www.bahn.com/
Transportation from Frankfurt airport to Darmstadt and/or Dieburg:
You can take the AIRLiner Bus from Frankfurt airport terminals to Luisenplatz or Darmstadt Central Station. From there you either take the bus 671 or the regional train to Dieburg.
If you are staying in Dieburg, you can take a regional train (RB75) from Darmstadt Central Station to Dieburg Station which will take 15 minutes. (Check the schedule here http://www.rmv.de/en/ or here https://www.bahn.de )
You can also take a bus (Bus 671) from Darmstadt Central Station to any station in Dieburg as well as Groß-Umstadt which will take 40 minutes. (Check schedule here: http://www.rmv.de/en/)
If you are interested to take a cab from Frankfurt Airport to Dieburg, the drive usually costs 97€, but you can ask for a special rate of 55€). It is advisable to share the cab with other participants and pay together.
Please reserve at least 24h in advanced at Dieburg’s taxi service. Phone Number: +49 6071- 33333
From Frankfurt airport to Groß-Umstadt:
Renting a car is also a possibility. Parking on Mediencampus is easy and for free.