Busses from the main station of Groningen (Groningen Hoofdstation) go every ~2 minutes. You can take the next lines to the venue:
The easiest place to park your car near the venue is the Centrum (Groningen) Parking (external website). This parking is opened 24/7 and costs €22 per day.
There are various trains going to Groningen. For the up-to-date times the easiest is to check the signs at the airport. The platform the train is leaving from is either 1, 2 or 3. There are two trains, of which one has a transfer in Zwolle, the other one is direct. Both are the same price (€25.30 for a single ticket) and take respectively 2h 29m and 2h 09m.
Groningen Airport is about 15km from the citycentre. There's a shuttle bus (line 100) going to the city centre, which connects flights from London, Copenhagen and München. There's also a regular bus (line 9) which takes about ~35 minutes to the main station.