You did not indicate that you have activated sharing on your MacBook Pro. Assuming that you’re using a newer version of MacOS, you need to go to System Preferences > Sharing and check the media sharing box.
Alternately, if you are running an older version of MacOS, you would turn on Home Sharing in iTunes. The AppleTVs as well as any other Macs or iOS devices on your network should then be able to access the media on your Macbook Pro.
On the AppleTV, you access a shared library with the Computers app.
