Create a standard reference for the book. This helps readers find and use the source easily. If you are quoting or praphrasing information from the book's appendix, mention that in your in-text citation. For example, your in-text citation will look like this:
(Melnyk & Fineout-Overholt, 2019, Appendix B)
You can see more examples, like citing a table or figure from an article, on the APA Style page about citing specific parts of a source.
