You can search for topics using the Search Bar at the upper-right of the Britannica Online Premium home page. After entering your search term and clicking the "Magnify Glass" icon (or hitting the Enter key on your keyboard), you will be taken to the Search Results page.
As shown in the image below, searching for the word "Chicago" brings up a number of different search results. After looking over the results that are displayed, you may find an article that you would like to read. If you place the mouse cursor over the first article selection to highlight it, you will be able to view the "Table of Contents" in the right-hand column for this article. To view the Article Page simply click on the title of the article.