Hi,
You have to un-pair (or disconnect ) the Flip from the first device.
Press the Start button on the JBL Flip, it will make a warning beep and turn on. The start button will glow blue.
Press the '+' and '-' buttons together, and press the 'Bluetooth' button on the JBL Flip, and keep pressed until the Bluetooth button starts blinking blue. Now the JBL Flip is in pairing mode and can be discovered by the new device.