Whenever you use someone else's ideas in your own work, whether it be a direct quote or paraphrase, you must cite that source in your text.
Your in-text citation should include the author's last name and the page number where the quote or information can be found.
If you use the author's last name in the sentence, just include the page number.
According to Casey, "libraries are a space for inquiry and learning" (194).
There are many ways to cite an author or authors within your text. For more information on in-text citations, see pages 54-58 and 116-127 in the MLA Handbook.