So, if you type in "Lorado Taft" it will bring up every PDF that mentions Lorado Taft in the University Archives.
In the search results, once you click on one of the PDF filename links, a PDF will open.
Once within the PDF. you can also do a (keyboard command) CTRL+F to search for a specific key word.
On the PDF in the upper left hand corner is a record series number. If you wanted to look up the Lorado Taft Papers that would be record series number 26/20/16.
From looking at this PDF, you can gather a general idea which Record Series Number, Box Number, and Folder Title that is of interest to your topic.