In general, just enter the topic that you want to search into the search box. Adding more terms or words won't necessarily improve your results. For example, if you are interested in in gun control, just enter "gun control" with the quotes. Using quotes will search for that phrase giving you results that are more relevant to your topic.
The Opposing Viewpoints Series is a good resource when you want to look at various topics and find essays that cover both sides of an issue. The essays tend to be short--5 to 10 pages--and cover various positions and options related to a given topic-for example, gun control. They are not in one location, but can easily be located by searching for "Opposing Viewpoints" in the catalog or by clicking on the link above.