Citing the DSM is covered in Sections 10.2 and 10.3 of the APA Publication Manual, and online.
Entire volume DSM citation (follows BOOK format):
American Psychiatric Association. (2022). Diagnostic and statistical manual of mental disorders (5th ed., text rev.). https://doi.org/10.1176/appi.books.9780890425787
Entry in the DSM (follows BOOK CHAPTER format):
American Psychiatric Association. (2013). Anxiety disorders. In Diagnostic and statistical manual of mental disorders (5th ed.). https://doi.org/10.1176/appi.books.9780890425596.dsm05