Dissertation proposals are like summaries of your research and will help you explain what you are going to research and, roughly speaking, how you are going to collect and analyze your data. Your thesis proposal will help you identify and define both of these things, as well as allow your department and faculty to ensure that you are recommended by the best person to help you complete your research. There are no particularly strict rules when it comes to the format of doctoral proposals—your supervisor will be more than able to guide you through the process. Basically, there is little difference in approach to a PhD, except that you should present a deeper methodological section, and perhaps be a little more critical of the existing literature in the literature review section.