In MLA, this is called "Indirect Sources," and you are advised to locate the original source and cite that when possible. If the original is not available, in-text citations use this format: (qtd. in Jones: pp) where Jones is the second source author's name and pp is the page number. Then you cite it normally in your works cited list.
Here is the section of the MLA Handbook (9th edition, page 284) with this information:
Wherever you can, take material from the original and not a secondhand source. But if you quote an author's quotation of a source you did not personally consult, put the abbreviation qtd. in (for quoted in) before the indirect source you cite in your parenthetical citation. The abbreviation qtd. in is not needed if your prose makes it clear that the source is secondhand. (Otherwise, you can clarify the relation between original and secondhand sources in a note.)
Quoted in your work
Samuel Johnson admitted that Edmund Burke was an "extraordinary man" (qtd. in Boswell 289).
Work cited
Boswell, James. Boswell's Life of Johnson. Edited by Augustine Birrell, vol. 3, Times Book Club, 1912.