Format: 

Author, A. (Year, Month Day). Title of work. Title of Proceeding, Volume, Pages. http://dx.doi.org/xxxxx or Retrieved from URL

Author, A. (Year). Title of work. In A. A. Editor (Ed.), Title of Proceeding (pp. xxx-xxx). Location: Publisher.

Examples: 

Perkins, E. (Chair) (2013). 2013 1st IEEE conference on technologies for sustainability (SusTech). Piscataway, NJ: IEEE.

In-text: (Perkins, 2013, p. 6)

Notes: 

If a conference proceeding is published regularly, cite it as you would a journal article. If the proceeding is published in book form, cite it as you would a book chapter.

Source:
APA - 7.02, no. 38-39
APA (ER) - no. 36-37