Check out this Apple article -> Using AirPlay
Enabling AirPlay from iTunes on your computer
To stream music or videos from your computer to an Apple TV or AirPort Express:
- Connect your computer and Apple TV to the same Wi-Fi network.
- Open iTunes (10.2 or later).
- Locate and click the
icon in the bottom-right corner of the iTunes application.
- Select your Apple TV, AirPort Express, or AirPlay-enabled speakers or receivers from the list of available devices that appears, and begin playback.
Note: The images of a TV screen
or speaker
next to each AirPlay device in the AirPlay menu indicate the type of media content you can stream to that device.
Do you see the Denon when you click the AirPlay icon in the lower right corner of iTunes?