When you reproduce a part of a text word for word, you must include the page number of the quotation in your citation. It might also be a good idea to include the page number when you paraphrase (using your own words) from a longer text, e.g. a book or a book chapter. The page number will make it easier for your reader to find the relevant passage in the source.
You can read more about paraphrasing and page numbers in APA:s blog.