[Tracker]

Could you be more specific please? Actually you're trying to steal from the brotherhood, which is a bad idea, but also a plot element. When you're in your cell awaiting your initiation, you need to push the table under the window, and see which continent floats on the sky (it can be things like 'Aristagon', etc.). Now if you did everything correctly, you must have a paper with a sentence written on it. Choose the word which begins with the same letter as the name of the continent. Leave the room. Now you're standing at a wall with coloured hands carved in it. Each hand is made from a jewel, they all have different names. Hover the mouse on them to see their names. You need to press them in a certain order. Look at your paper again - you choose a word which begins with a certain letter. Now you need to press the hands which names' begin with the letters in the word. If the word was something like 'and', you'd press the hands saying 'amber', etc.
Now the treasure room opened. You see a statue there standing in red light. Cast a spell you learned from the small toy that walked on the street in the beginning. The statue will walk forward and collapse. Pick up the green necklace. Put it on the table in the middle of the room. Now the treasure appears. Grab what you need to. When the thieves enter the room, take the necklace from the table, and the thieves will disappear. Now you succesfully stealed from the Dark Brotherhood's treasure room and defeated the thieves!
Well, if this didn't help you, feel free to use the walkthrough.