What research question will you choose to pursue?
You started with a broad topic idea, such as 'children and aggression.' Now that you've read a reference article on the topic you will be able to select and identify the possible ways you can focus your topic into something more manageable. If your topic is too broad when you begin searching, your search will result in too many articles. Refining your search before you get started will allow you to find a list of results that isn't too overwhelming.
Keep in mind that each time you find more information on your topic you may decide to refine your topic a little more. That's ok! It's all part of the process.
NOTE: If you were actually going to write a research paper, you would think of a research question based on your reading of the reference article, such as, "Are there any prevention programs that schools have used successfully to reduce violence in schools?" The answer to your question would form the basis for your paper's thesis statement.