Citing chapters of a dissertation in APA Style
Since one person wrote the dissertation, you don't need to break out the chapters because your in-text citations will point people to the relevant sections of the text. If you made mention in your text that you used specific chapters, that also makes it clear to your reader how you found the information, but again, you don't need to reference the sections separately.
Regarding the format of the reference, please see "How do I reference a PhD dissertation or MA thesis in APA style?".
American Psychological Association. (2010). Publication manual of the American Psychological Association (6th ed.). Washington, DC: Author.