Choosing a topic can be the hardest part! Here are some tips:
Read your assignment again. Sometimes it can clue you in to some topic ideas
Choose something that interests you
Look at your textbook's table of contents or skim your chapter
Talk to your instructor
Talk to your classmates
You can even try searching GOOGLE or your favorite search engine. Put in some terms for your broad topic and see what kind of results you get. Anything look interesting?
Once you have a topic, write it down as a sentence or a question.
Check out this great video from NC State Libraries about the research process.