You can reach Münster directly via highway (Autobahn) A1 and A43. Driving from Frankfurt, Hamburg or Amsterdam to Münster takes about 3 hours, driving from Berlin around 5 hours.
From the north of Münster:
On A1 highway take the exit (Ausfahrt) Münster-Nord (77) towards Münster, Gronau, Steinfurt, Havixbeck keep left on Bundesstraße B54 in the direction of Münster.
Follow the Bundesstraße B54 for 3,5 km (Steinfurter Straße) until you see the Schlossplatz on the right.
After 500 m you can turn right towards the public parking spaces of the Schlossplatz.
From the south of Münster:
Take either A1 or A43 highway.
From the A1 take the right exit at the Münster-Süd interchange (78) and follow the B51 in the direction of Münster, Warendorf.
From the A43 just drive straight until it becomes the B51 in the direction of Münster, Warendorf.
In both cases, the B51 goes over into the B219 which leads straight into the city. You are now on the Weseler Straße. This street leads to the Am Stadtgrabe after passing the Aasee (lake). Follow this street until you arrive at a large crossing with traffic lights and you are able to see the Schlossplatz on the left. Turn left here onto the Gerichtsstraße and take the first road to the right towards the public parking of the Schlossplatz.