This service is staffed by librarians at ARC and the rest of the world. So, great for getting quick answers to quick questions, but if you want to talk with a librarian who is already familiar with the assignment and the ARC library, please use my contact info above.
I kind of hate OneSearch. I don't think it works very well. A lot of the time it will get you what you need, but a lot of the time it won't. If it's not getting you what you need, please try another database and/or let me know so I can help :)
If you're not sure what theme you want to write about, I suggest just searching for the author and the some keywords from the title of the short story. For example:
henry gift magi
That way you can see what other people are writing about and that will help you pick a theme you want to discuss.
If you have a theme in mind, try adding a keyword for that theme to the search. For example:
masque red death poe mortality