cant find airplay late 2011 macpro running el cap

I'm trying to find airplay on my 2011 Mac Pro, running el capitan, 512 SSD Crcial drive, w 4 GD RAM Cache, plenty of room in memories, can't even locate airplay. In Display, it will not toggle to "ON", only "Off" apppears,

Help... Id like to mirror from apple tv 4th gen I just got.