Q: airplay display

ok, now i up date it to 10.10  and still not working. how can i make it turn on?

I go to Open display preferences , try to turn on the apple tv option, takes a minute or two , and later it says could not connect to apple tv, whe i have everything set and turned on , my apple tv and my itunes are paired . thank you!

well that might be the problem, but do i know how to change that? nooop . help please !