While you know the topic you will be researching, you still need to narrow the topic and formulate a specific research question that you will answer.
Mind maps are a great tool to help you organize your thoughts and see new information or connections that you might not have previously been aware of. As you develop your mind map, narrow your topic down from a broad topic to a specific research question. You will use this research question, and the keywords you've identified on your mind map, to search the library databases for resources. As you utilize the research databases, continue to fill in information on your mind map to help you see if there are gaps in your research that you need to address.
Example Mind Map - topic: Fake News
First, you develop and narrow down your topic -- the general idea of what you're going to be researching. From that, you need to develop your research question, i.e. what is the question you are attempting to answer by doing your research? This, in turn, will form the basis for your paper's thesis (your claim/argument/answer) which you'll explicitly state in your introduction.