The MLA has not yet prescribed a citation format for YouTube videos. The example below is based on the format recommended by Purdue University's Online Writing Lab (OWL) website.
IT: (University of Lethbridge Library)
WC: University of Lethbridge Library. "The Book2Net Spirit book Scanner, in your Library." Online video
clip. YouTube. YouTube, 30 Jan. 2015. Web. 6 Mar. 2015.
NOTE: For works with no page numbers, such as YouTube videos, it is preferable to include the author's name in the text and omit a parenthetical reference altogether.
The date at the end of the works cited citation is the date of access.