This is a good question. It is important for you to learn to cite your sources correctly. I am assuming you are referring to the e-notes study guide. You will find that all e-notes study guides do provide you the information for proper citation. Right under the title of the page (for example, "She Walks in Beauty: Introduction") you will see icons for printing, PDF, citing, and sharing. Click on the "cite" icon and a window will open giving you the information you need. There are several pages in the study guide for "She Walks in Beauty" so be sure to cite each specific page that you use.
Here is the citation that occurs when you click on "cite" under the introductory page of the guide:
Cite this page as follows:
"She Walks in Beauty: Introduction." Poetry for Students. Ed. Marie Rose Napierkowski. Vol. 14. Detroit: Gale, 1998. eNotes.com. January 2006. 5 July 2011.