If you have found (or been given) a book or article that is very relevant for your topic, review the list of references (the sources used by the authors). Some of these cited works may be helpful to you also. To find cited books or articles, where you look depends on what it is:
Is it a book (or book chapter or government document or videorecording)?
Is it an article (in a journal, magazine, or newspaper)?
The "How to Borrow from Other Libraries" guide explains how to get materials unavailable online or in Andersen/Lenox (Rock campus) libraries.
Suppose you need to find this:
Katz, E., Blumler, J. G., and Gurevitch, M. (1973). Uses and gratifications research. Public Opinion Quarterly, 37, 509-523.
You can find it by searching Research@UWW "Everything" for "Uses and gratifications research" or by doing a journal search for "public opinion quarterly." In either case, click "Online Access" to get a link to the full text article in JSTOR (under "View Online").