There are direct TGV trains from Paris (and St-Exupéry airport) that come to Grenoble. When you come out of the station you can catch a Tram that will take you to the campus. Be sure to catch the tram on the "B line" going in the direction of "Gières/Universités". Step down from the tram when you get to the tram-stop "Gabriel Fauré".
If you are coming from Lyon (motorway A48) or from Gap/Sisteron (N175/N185), follow Chambéry, Rocade Sud. If you are coming from Chambéry (motorway A41), follow Lyon, Valence, Rocade Sud.
Take the first exit on the "Rocade Sud" and you will reach the Campus of St Martin d'Heres.