Go to the configuration menu of your smartphone:
iOS (Apple):
From the main page, click on the "Settings" icon.
Then click on "Bluetooth™".
Activate the button (it should turn green).
Then, choose the name corresponding to your vehicle (in this case, BT_DS) under the "Connect to my devices" list.
ANDROID:
Swipe up and down the screen or access via the Settings menu.
Press Bluetooth™.
In the list of devices, select the device corresponding to your vehicle starting with BT_
I lost the Bluetooth connection between my smartphone and my vehicle
If you have lost your Bluetooth connection, turn it off and repeat the procedure above.