from where dear?
from Colombo you can get a bus to Kollpety then take kolpetty-kaduwela bus. and its going in front of SLIIT, Ask the conductor to stop at SLIIT.
Or from kandy - colombo dorection, you can either get down from Belummahara/Miriswathta & get on to a gampaha kaduwela bus or from kiribathgoda, to kiribathgoda- kaduwela bus. then fro kaduwela get ont oa kaduwela malabe bus & get down at SLIIT