If it's a standard 5 paragraph essay then you could write two paragraphs about the similarities. Think about an event or the characteristics of the people of the stories that are similar and how they relate to one another. You can do the third body paragraph on something that is different between the two stories, it can be the setting (time, place, etc), or the different language used. From there the intro and conclusion are cake. You can message me if you have any more questions.