Style:
Author, A. [username]. (year, month day). Title of video [Video file]. Retrieved from http://url

Example:
Bass, L. [lenbass]. (2016, July 31). Networking [Video file]. Retrieved from http://presentationtube.com/watch/?v=zFZAGr8vLfJ

Source:
http://blog.apastyle.org/apastyle/2011/10/how-to-create-a-reference-for-a-youtube-video.html