You will need to start the paper with information about the field itself:
Provide the definition of the applied psychology discipline chosen
Describe what kind of training is required to work in that field
Identify where these professionals work
Review the work performed by these psychologists, including the type of research in which they engage as well as the application of this research

Then an overview of the research study related to the field you found. This should be about half of the paper in terms of content.