The first section of your essay should discuss 3 periods of Mr. Northrup's life (freedom, enslavement and post slavery).
The second section of the essay explains how the movie shed light on the resilience and character of African Americans(free and slaves), Southern plantation owners, the white community, and Northern abolitionists during this time period, 1830-1865.
The third and final section is your personal reflection and the movie's impact on your mental psyche.