Example of how to quote footnotes.

You need to cite the source the same way  you would any source.  In this case the author is the editor of the edition: William Attridge et al.

“Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut” (Attridge et al 256).

or

Attridge et al in the Harper Collins Study Bible, write: “Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut” (256).

The bibliographic entry that would follow the above example would be as follows:

• The Harper Collins Study Bible. Ed. William Attridge et al. New York: Harper Collins, 2006. Print.