From Toronto:

GO Train from Union Station to Ajax GO Station, 
Durham Transit Bus (No. 915 East) from Ajax Station direct to Ontario Tech University Campus.

Train and Bus schedules are available at: 
GO Schedule 
Durham Transit 
Select schedules from Toronto to Oshawa and vice versa. Choose "Lakeshore East" from the pull down menu. 

Please note that the cloest airport to Ontario Tech University is Toronto Pearson International Airport.

Ground directions between Ontario Tech University and Airport / Train Station:

You can use public directions to move from airport to reach Ontario Tech University, and to train station: See Details