Think of Wikipedia (and all other encyclopedias) as pre-research.
So go ahead and start here by reading an encyclopedia article about the topic you are interested in or skimming several articles to decide on a topic. These articles will give you many pertinent facts (who, what, when, & where) that you can use as keywords when you begin researching.
Yes, Wikipedia is a free, publicly-authored encyclopedia that professors love to hate. However, peer reviewed research has demonstrated that Wikipedia articles are usually as reliable as and less biased than World Book Encyclopedia or Encyclopedia Britannica.