It works best to first disable Bluetooth on your phone, so the two Turtleboxes have time to pair together before one syncs with your phone. Next, turn both boxes on and push the "2 Bluetooth" button on either box.  When the two boxes stereo pair, you will hear a loud beep and the 2 Bluetooth button on one box will be solidly lit.   Then, turn Bluetooth on your phone back on.  Please note that the first time two boxes have paired, it can take a minute or two for them to find each other, and you may have to turn the boxes off and back on and try again.   After the first time they pair, they will instantly pair from then on.