Go to Settings -> Bluetooth. Switch the Bluetooth button on. Have your other Bluetooth device in pairing mode, and allow your phone to search for the device at the same time. Once your phone and Bluetooth device has detected each other, confirm that you want to connect. Sometimes you’ll receive a pairing code to verify the connection, so if it does match with the other device’s pairing code then it should be safe to connect. After the connection is set, your Bluetooth device should connect with your phone. Assuming that your phone’s Bluetooth switch is turned on, your other Bluetooth device(s) will automatically connect with your phone once they turn on after the initial pairing.