Usually it is no problem to find a parking space. Walk to the science building. For a campus map see further down on this page. Buy a train ticket to Nijmegen-Heijendaal. They do accept credit cards there but not in all other train stations.
Trains run about four times per hour.
The platform is upstairs from where you arrive. Once per hour the train runs through to Nijmegen Central Station. Once per hour you have to change trains in Arnhem. Go North, direction Amsterdam and Utrecht. That puts you on A50.