You do not have make any settings changes in Vlingo to use Vlingo over Bluetooth. Vlingo uses the default Bluetooth setting of the iPhone found at Settings > General > Bluetooth > Bluetooth On/Off. If you have an A2DP Bluetooth head set that you are able to use with your iPhone, then you can use Vlingo over Bluetooth.
At this time, you cannot activate Vlingo using your Bluetooth headset activation button. You will still need to open Vlingo and tap the "Press and Speak" button to speak to Vlingo to over your Bluetooth headset.