The main window in Airfoil contains all its essential controls. To send audio to an AirPort Express, select an audio source from the Audio Source Popup at the bottom. Then, click the Transmit button next to each AirPort Express to which you wish to send audio. Finally, play audio in the audio source, and it will be transmitted to the selected AirPort Express units.
Main Controls
Remote Speakers List - Displays all available AirPort Express units, as well as volume and transmission controls for each.
Level Meters - Meters showing audio activity for the currently active transmission.
Audio Source Popup - Sets the audio source from which Airfoil will pull audio.
Effects Button - Toggles visibility of the Effects window