Browse through an Encyclopedia for topic ideas.
Also look at World Eras encyclopedias.
The search box default is "basic search". This is a keyword search and often the best search. You can also change the drop down menu to "subject", for fewer results but sometimes better results.
Look at "Filter Your Results" on right side of results page. Try Filtering by Subject and Document Type. The "excerpt" document type can include primary sources, sometimes excerpts, and sometimes the entire document.
Also look at "Search Within" to find a more specific topic within your search results.