It's great that you want to cite enotes in your work. For standard MLA citation, see below:
An Article from an Online Database (or Other Electronic Subscription Service)
Junge, Wolfgang, and Nathan Nelson. “Nature's Rotary Electromotors.”Science 29 Apr. 2005: 642-44. Science Online. Web. 5 Mar. 2009.
Langhamer, Claire. “Love and Courtship in Mid-Twentieth-Century England.” Historical Journal 50.1 (2007): 173-96. ProQuest. Web. 27 May 2009.
All you need to do then, is to feed in the information. The author is Ira Mark Milne.
Milne, Ira Mark. "Introduction." Drama for Students. Vol. 24. Gale Cengage, .eNotes.com. 12 Nov, 2012
As an in-line citation, just use 'Milne' - the first website below shows you in more detail how to achieve this.