where are you located? I am assuming Europe. diesel engine. Over here you can go to any franchised auto repair shop and ask them for a diagram for the way your belt fits around these pullies. Usually they give it for free. I am not sure about your particular country but also BMW dealer can give you a print out of the same if you ask him in polite manner!!!
I am assuming you've tried to fit the belt over the pullies but you ran out of pullies with 12 inches of EXTRA belt!! If so I can hand-draw a diagram for you. let me know