Format: 

Author, A. A. (year). Title of doctoral dissertation or master's thesis (Doctoral dissertation or master's thesis). Retrieved from URL

Author, A. A. (Year). Title of work (Doctoral dissertation or Master's thesis). Available from Database Name database. (Accession number)

Examples: 

Hensel, E.C. (1986). Multi-dimensional inverse heat conduction (Doctoral dissertation). Retrieved from ProQuest Dissertations and Theses database. (UMI No. 8629867)

In-text: (Hensel, 1986, p. 7)

Steinke, M.E. (2002). Heat transfer, pressure drop, and dissolved gas effect during flow boiling in microchannels (Master's thesis). Retrieved from http://scholarworks.rit.edu/theses/5779/

In-text: (Steinke, 2002, p. 51)

Notes: 

Identify the work as a doctoral dissertation or master's thesis in parentheses after the title. Include either the name of the database and the accession number, or, the URL (e.g. institutional repository) at the end of the reference. If the document was completed at one school, but is hosted by another, include the name of the original university in the parenthesis after the dissertation/master's statement (e.g. Doctoral dissertation, Rochester Institute of Technology).

Source:
APA - 7.05, no. 40-44
APA (ER) - no. 38-40