Milgram's experiment demonstrates the importance of norms in human behavior because as the goal in the experiment is to have someone give up their seat voluntarily to a younger person with no illness as anyone would give up their seat to an elderly. Societal norms and signs in the public transit are visual to follow to give up your seat if there is a pregnant woman, a person with a wheelchair/ disabled, child and when these norms are acted against it sets the person up for discomfort, being embarrassed and guilty for not following the norm on transit. A possible situation that a researcher might use instead of the subway request would be instead of asking for the seat to sit down, ask for a seat to put your bag on, whether it be a big or small bag.
You are on the right track, but can you go into more depth as to why norms are important in human behavior? If you like you can even go into how a norm might be formed in society and what leads people to conform to it. Why is that important in human behavior? How might norms lead us to behave? These are all things that you can consider while answering the question.