If the editorial is signed by the editorial board, it is not necessary to indicate in a works-cited-list entry that the work you are citing is an editorial:

Editorial Board. “How to Tell Truth from Fiction in the Age of Fake News.” Chicago Tribune, 21 Nov. 2016, www.chicagotribune.com/
news/opinion/editorials/ct-fake-news-facebook-edit-1120-md-20161118-story.html.

If the editorial is unsigned and you want your reader to know that the piece is an editorial rather than a news article, you can refer to the work as an editorial in your discussion, or you can include “Editorial” as an optional element at the end of the entry:

“It’s Subpoena Time.” The New York Times, late ed., 8 June 2007, p. A28. Editorial.

If it’s an op-ed—that is, an opinion piece written by someone who is not an editor of the publication—you can include “Op-ed” at the end of the entry:

Gergen, David. “A Question of Values.” US News and World Report, 11 Feb. 2001, p. 72. Op-ed.