Other contributors have said "How do you put cape on lego vampire?" is the same question as "How do you put a Lego batman cape on the loose figure?" If you believe that these are not asking the same thing and should be answered differently, click here
How do you put a Lego batman cape on the loose figure?
On the cape, you bring together the two larger holes so that they are overlapping into one hole. Put the figure's neck through this hole - then attach the head.