It appears you are looking at older instructions, iTunes no longer has the option to look for apple TVs, it no longer needs it. Additionally, the new Apple TV's do not show in the device list in iTunes, which Apple TV are you trying to connect.
That depends on how you set it all up. If you chose the "connect to iTunes" option then you should be able to sync content to the hard drive on the Apple TV. If you chose the "add shared library" option then you can only stream to the Apple TV.