Setting in this case extends into two areas: the period of time Fredrick Douglass writes about in his story and the period of time in our nation's history when the book was published.
How is where and when (setting) important in telling the story? In your opinion, why did Fredrick Douglass choose this particular setting for his book? Find sentences from the text that you feel best describe the setting--then write about why you, as the reader, think these sentences are important in recounting the evils of slavery.
The question then asks for the impact of the novel on society. You will have to do some research on this part of the question. Search for book reviews, or historical accounts of how people responded to Douglass' book at the time it was published. I've provided a link which you might find helpful:
Good luck and great writing!