The first thing you want to do is to write an introduction that states your main thesis. There are many themes that you can choose from. Visit any number of websites to find the themes, then mold your essay around that. You could talk about the guilt that people feel when they have to kill people in a war situation. You could talk about how people retain their humaness in the face of such attrocities.
The story offers many examples and vignettes that can act as examples for your various paragraphs.
The conclusion will restate the thesis and summarize the information.