From this post I'll teach you how to download past papers.
First go to the Course Web, http://moodle.sliit.lk/.
Then login to the web. If you don't know how to login, please click here.
I hope now you know that. Then scroll down until you find the link 'SLIIT Digital Library' and click on it.
Then the past papers will appear in .pdf format. You can download them.
P.S - Don't wait till the last moment to download them, because when the exams are coming near, everybody is downloading them and the course web may seem to be very slow. My advice is that you better download them even before the semester begins and get some of them printed. During the semester, attempt the questions that you have been taught during the course. I have practically experienced that some of the questions in the past papers have been repeated and you'll feel confident when you sit for the exams and find such questions.