Using your iPhone, while listening to any show tap on the double-line icon next to the player controls to expand the player options. Click on the airplay icon which appears on the lower right, next to the volume controls. This will open Airplay streaming options from your device.
Using your iPad, swipe up from the bottom of the screen to open your iPad’s app tray. Then, slide the app tray to the right so you can see the volume and playback controls on the screen. From this area, if Airplay is connected, you will see the icon that will allow you to send your iPad’s sound to Airplay.