How do I correctly cite this reference in my research paper?

I am supposed to be using MLA format and I have no problem with the works cited, I just get so confused with in text citations after quotes. My problem arises whenever I quote something this is already quoted in the book I’m taking it from. Do I use the name of the author of the book with the page number or do I use the name of the person who actually said the quote with the page number? Also, when referencing a book with several authors, do I use the name of the person who wrote the specific section where my quote is coming from or do I cite one of the editors of the book?