It can be tricky to narrow down your topic so that you cover the subject sufficiently, yet provide enough substance and evidence to make your points clear and interesting. 

Ask yourself these questions:

• Are my ideas still too broad to be manageable?
• Am I trying to cover too many aspects of the subject?
• Do I need to redefine the main topic and sub topics?
• Do I need to revise the outline?
• In my preliminary research was I able to get a sufficient number of authoritative sources related to my specific focus on the subject? 
• Do I need to revisit and redirect my research strategies?
• Am I ready to begin thinking about my thesis (controlling idea)?

See documenting research to be sure your format is appropriate.