Distill your topic down to two or three keywords. The Library Catalog works differently from Google; that is, you can't type in a question or a long research statement and get great results.
ex thesis: The fall of Rome was, in part, indirectly caused by Emperor Constantine's conversation to Christianity
search terms: Rome | Constantine | Christianity
Navigate to the Library's Catalog (https://library.nmhschool.org/) and click on the "Advanced" option. Once in the "Advanced Search," input your search terms, hit "search," and cross your fingers!
Look through the search results for titles that look helpful to your research
In the search results, click on a relevant title to see the catalog record for that item. Look for clues that will help you decide if this source will be good for your research, such as publication date, a table of contents, and finally, the call number and location of the book in the Library.