Tap on the '+' icon to add device. It will show 'Searching'; and the bar at the bottom of the icon will be blinking blue.
After searching, a list of Bluetooth devices which you have paired before will be displayed. Tap on the device that you want to add to the Widget. Note: Make sure the Bluetooth feature of the device is on.
Tap on the device icon to start the pairing. After paring the bar will be blue.