From Paris airports, take a train to Rouen at Gare-Saint-Lazare : they go every hour or so and cost about 20€ one way.

From Rouen train station, walk out and take bus F2 up to Mont-Saint-Aignan and stop at Place Colbert.

With a taxi, ask for the University at 1 rue Thomas Becket in Mont-Saint-Aignan.

Then, look at maps of the campuses at the entry of the main campus.