Citing all your sources is mandatory in academic research. If sources are not cited correctly, or worse, not at all, accusations of plagiarism might result. To avoid this, view the videos and follow the specific APA examples found through the links below. For Psychology, the APA (American Psychological Association) style is usually the preferred style.
From Purdue University's Online Writing Center (OWL).
Publication Manual of the American Psychological Association by 
Cite Right: A Quick Guide to Citation Styles by 
The Complete Guide to Referencing and Avoiding Plagiarism by A video from Editage, a professional editing service.
Student Guide to Research in the Digital Age by 
Writing Research Papers: A Guide to the Process by 