If you want to get from the main train station to the centre of Lausanne, take a train to FLON (one stop uphill) and then the subway to EPFL. Travel time from the main train station usually does not exceed 30 minutes.
When travelling by car, make sure you follow signs to "Lausanne-Sud" from the highway stretching around Lausanne and Geneva. Take the exit marked "Universite E.P.F.L." and follow signs to EPFL.
After landing in Geneva, choose one of the regular trains to Lausanne. This takes about 30 minutes.