To cite your sources in APA, you first need to understand the anatomy of a citation.
An article citation might look this:
Author, A. A., Author, B. B., & Author, C. C. (Year). Title of article. Title of Periodical, volume number(issue number), pages.
Pickering, G. J. (2009). Optimizing the sensory characteristics and acceptance of canned cat food: Use of a human taste panel. Journal of Animal Physiology and Animal Nutrition, 93(1), 52-60.
A citation for a book might look like this:
Author, A. A. (Year of publication). Title of work: Capital letter also for subtitle. Location: Publisher.
Mayr, E. (1982). The growth of biological thought: Diversity, evolution and inheritance. Boston, MA: Harvard University Press
A citation for an article or chapter in an edited book might look like this:
Author, A. A., & Author, B. B. (Year of publication). Title of chapter. In A. A. Editor & B. B. Editor (Eds.), Title of book (pages of chapter). Location: Publisher.
O'Brien, C. (2005). Drug addiction and drug abuse. In L. B. Brunton, J. S. Lazo, & K. L. Parker (Eds.), Goodman & Gilman's The pharmacological basis of therapeutics (11th ed., pp.607-629). New York, NY: McGraw-Hill.
Different types of publications (articles, books, conference papers, book chapters, edited books, etc.) include different elements. The elements required for a particular type of citation are those that allow a reader to find the source you cited.