Press and hold the button for 10 secs (should should hear a short beep at 10 seconds). This will place the device in discoverable mode. (Advertising mode).
KEEP IN MIND: In iOS and Android platform, you cannot use the Bluetooth Settings menu to pair to a BT 4.0 device. You must use a BT 4.0 specific App to pair (by developing your self or downloading some demo app).
I recommend you compile a sample application available for BT 4.0 device to get started.