The in-text citation for the DSM would look like this:
(American Psychiatric Association, 2013)
If you're citing only a certain entry, you might include the page number(s):
(American Psychiatric Association, 2013, pp. 190-195)
In that case, the reference (at the end) would include the section name and page range as well, for example:
American Psychiatric Association. (2013). Separation Anxiety Disorder. In Diagnostic and statistical manual of mental disorders: DSM-5 (5th ed., pp. 190-195). Washington, D.C.: American Psychiatric Association.
I hope that helps. Please write back if you have any further questions.
Sincerely,
Michael Davidson
Lamson Library