Summarize the following:
Most of the time, you can search an online encyclopedia by entering search terms in a search box on the main page. Pick something that seems to embody your topic to get the most relevant results.  For instance, to research the Civil War, you might enter "American Civil War." Refine your search as needed. For instance, you might have to change "American Civil War" to "U.S. Civil War." You can search within a specific site using Google's search box. This method can be helpful if the site doesn't have a search box, or it doesn't seem to be returning relevant results. Start with your search terms, followed by a space and "site:" followed by the name of the site. Google will only turn up results from that encyclopedia site. For instance, if you want to search for the Civil War on encyclopedia.com, you'd type "Civil War site:encyclopedia.com." You can also find information by simply browsing, if the encyclopedia is set up for that function. To browse, look for the list of broader subjects, and narrow down to a topic that is relevant to what you want to research. For instance, if you're interested in the Civil War, start with "History" in a general encyclopedia. From there, you might click "American History" and then "Civil War."

Summary:
Use the site's search box. Try Google's search box. Browse by subject.