APA citation style refers to the rules and conventions established by the American Psychological Association for documenting sources used in a research paper. The APA Citation Style is often used for courses in psychology, education, business and other social sciences.
A free tutorial is available on the APA Website:
Basics of APA Style - comprehensive, 23 minutes; click on left side menu of the tutorial to go to exact section you need help with.
DOI numbers are now required for APA citation if they are available. For example, DOI:10.1177/0022042618759487. Otherwise, you should include the web address in your citation. For more information on how to find a DOI number, follow link below for a tutorial from the APA Style Blog: How to Find a DOI
Writers Handbook - APA documentation style from the University of Wisconsin-Madison Writing Center.
Online Writing Lab - from Purdue University. Lots of advice for writing, tips and examples on paper setup, as well as APA citations.
Guidelines for Writing in APA Style - From Southern Mississippi University. Lots of examples for print resources. Good outline for formatting papers and general guidance as well.