The prospectus is basically the first three chapters of your dissertation, but verb tenses are about the future, i.e. "this study will...."
The first chapter is your introduction, stating the problem your study will explore, your research questions, definition of terms, delimitations, and significance of the study.
The second chapter if your literature review, in which you provide background on each concept that the reader needs to understand in order to evaluate your study.
The third chapter if your research design and methodology, both for data collection and analysis.
I think that different disciplines and different academic programs may have different requirements for these three chapters. Ask your dissertation advisor for recommendations. Ask to see the dissertations of other students in your program that were particularly well done.