Go to QuickSearch, and click "Browse by Subject or Call Number."
From the drop-down menu, select either "Browse by subject" or "Browse by call number - Library of Congress." Here's what these options will do:
If you select Subject, then enter in your terms. For example, if you want all items tagged with "Benjamin Franklin", enter it with the last name first.
If you select Library of Congress call numbers, then enter in the first line of a call number. For example, "E300" will find books about American History during the Revolutionary War, mostly about the early presidents.
Review your results. For the Subject search, you will see many variations on the same term. Look at the number of records attached to that term, and click the one with the most records. Or if you see one that is more specific and looks perfect for your topic, try that one!
For the call number search, you will see a list of physical books in the library organized by the call number. Since call numbers represent a subject, your results should be about the same topic. Review the list and click any books you're interested in!