Picking a topic is never the easiest thing to do. The exercise shown above is a great way to go about this. Your instructor more than likely has given you a general idea of a topic: campus life, histories' mysteries, community. Those are all really big, so where do you get an idea to write three to five pages?
The idea is to get as many words related to the general topic, and words related to the new words as you can. Once you've done this, and if you made a big web like the example above, you can almost read a question from the words you put down!
Not only that, but when it comes time to actually look for sources for your work, these mapped words act as keywords! Now that's working smart.