To cite a biographical note, mention it in your prose and then include the work in your works-cited list:
According to a biographical note in Edith Wharton’s The Age of Innocence, the author “was born . . . into such wealth and privilege that her family inspired the phrase ‘keeping up with the Joneses.’”
Wharton, Edith. The Age of Innocence. Barnes and Noble Classics, 2004.
Published 25 May 2018