You have already established two aspects of your focus which is to compare/contrast the setting and symbolism of two stories, but on the surface, these two categories might seem unrelated and therefore difficult to tie to each other in the same essay. The best way to make this work is to choose one common theme subject which both stories share and show how each author uses both symbolism and setting in order to portray this theme.
Once you've decided on a theme subject, the best way to begin any essay is to brainstorm lists of ideas of things on which to write. Start by asking yourself (and answering using the text as evidence) the following questions:
- What is the setting of each story and how does each author use the setting to portray [chosen theme subject].
- What are 2-3 symbols in the story and how does the author use symbolism to portray [chosen theme subject].
Based on the list of ideas you brainstorm, you should be able to see where logical organizational breaks occur. Based on my experience, there is usually far more evidence in support of symbolism (for almost any story) than setting, so my final piece of advice is to see if you can't look at the setting of each story as symbolic in some way. Then, you are basically looking at one theme, two stories, and how symbolism is used in each.
If you need ideas while brainstorming, I encourage you to post a more specific question using the "Discussion" forum here on Enotes. Good luck.