Use the word and followed by the year in parentheses when citing a study written by two authors:
as Kurtines and Szapocznik (2003) demonstrated…
If the authors are not part of your narrative, acknowledge them by writing their names joining them with an ampersand followed by the year of publication. Insert a comma between the last surname and the year.
as has been shown (Joreskog & Sorbom, 2007)
(American Psychological Association, 2020, p. 266)