I have got little things to do at work?

Definitely talk to your supervisor, I am uming that one of the people who interviewed you is now your current supervisor? If so that would be easier. Tell him/her that you have gotten down what you have been doing the past 2 months and are ready for more ignments related to x and y (whatever you guys talked about in the interview). I know you are frustrated but give them a chance to explain themselves. It could be that your boss just didnt have time to train you on something they wanted you to do, and this will give them the gentle push they need. What things they were thinking for you might be a surprise to you (in a good way).