A lot of useful tips can be found here: http://torun.jakdojade.pl/?locale=en
Taxi from both - Main Railway Station (Toruń Główny) would cost ~25 PLN.
Faculty of Physics, Astronomy and Informatics
Grudziadzka 5 street
87-100 Toruń, Poland
By Train (Main Railway station, Toruń Główny):
If you want to get from the Main Railway station to the Faculty of Physics, Astronomy and Informatics take a bus number 22 or 27. Get off at bus stop named "Aleja Solidarności" (~7 minutes, 3th bus stop). From there you can walk - about five minutes. Look at the maps. Link to MZK Toruń if you want to check bus.
By Bus (Bus station, Dworzec PKS):
To get to the Faculty of Physics, Astronomy and Informatics you need to walk ~5 minutes to reach the conference venue (no bus or tram needed).