i have another computer set up with my apple TV and I added my computer to the apple TV, but I can't get it to see my photos. How do I fix this?

My dad originally set up his apple TV with his computer, but I want the photos on my computer to play on the screen saver on the apple TV. I added my computer to the "iTunes" tab under "settings", but my computer doesn't show up when i click on "screen saver" then "photos", my computer doesn't show up. The photo stream appears, but only a few of my photos show up, not all of those in the photo stream. I have already set up my iTunes to choose specific photos, but my cmoputer sdoes not show up under "photos" and the photo stream isn't working. How can I get this to work?

Thanks