Let's say you have used information from this article found in the Psychology Database Collection

APA tells you to include:
Author(s). (Date of publication). Title of article. Periodical Title,
volume
number(issue number), page
numbers. doi# .
So you write:
Klimoski, R., & Palmer, S. (1993). The ADA and the hiring process
in
organizations. Consulting Psychology
Journal: Practice and Research,
45(2), 10-36. doi: 10.1037/1061-4087.45.2.10.
Note: The DOI (Digital Object Identifier) number was not listed in the citation information we got from our initial results list. To locate this number, you may need to open the article itself where you will see the following information:

Unfortunately, you will not always be able to find a DOI number; some articles do not have them assigned. What then?