Use your iOS device (iPhone, iPad, or iPod) to stream internet based music (Spotify, Deezer, WiMP, TuneIN etc) or to stream music stored on your device. You can also stream music from your computer through iTunes. From an iOS device you can play one speaker at a time. Apple limitation. Using iTunes on your computer - you can stream to more speakers simultaneously.
With at least one AirPlay speaker connected to your Wi-Fi network, you'll see the AirPlay icon (a rectangle with a triangle pushing into it from the bottom) appear in your Music App and in Control Center (iOS) or in iTunes on your computer. Tap to select speaker and start streaming your favorite music through AirPlay.
Sometimes AirPlay can lose connection between your speaker and your device. Use Libratone App to check Wi-Fi signal strength on speakers location. Relocate speaker until signalstrength is 60% or higher.
Please also note that Wi-Fi connections may suffer from minor audio dropouts from time to time due to other devices in your home influencing your WiFi network traffic.