Arnhem is in the eastern Netherlands, close to the German border. The nearest major airport is Amsterdam Schiphol, about 1.5 hours by direct train.
By train, Arnhem Centraal is well connected. Direct trains run to Amsterdam (1h 10m), Utrecht (40m), Nijmegen (15m), and across the border to Dusseldorf and the Ruhr area. The station was redesigned by UNStudio and is worth a look in its own right.
By car, Arnhem sits at the junction of the A12 (The Hague--German border) and the A50 (Eindhoven--Zwolle). Distances within the Netherlands are short -- Amsterdam is about 100 km.
From the station, the city centre is a five-minute walk.