The Kenwood KDC-MP435U car receiver is billed as "Bluetooth ready," but in fact it cannot directly interface with Bluetooth phones. In order to turn the receiver into a hands-free phone device, you need an additional component, something Kenwood calls a Hands Free Box. This component is Bluetooth equipped and connects to the receiver via its disc changer input port. Once you've got the Hands Free Box installed, pairing it to your cell phone is a fairly simple matter.
Install the Hands Free Box and connect it to the receiver according to manufacturer's directions.
Turn on the receiver's control unit.
Have your cell phone search for nearby Bluetooth-compatible devices. This is normally found in the Connections section of your cell phone's General Settings menu.
Select "KCA-BT100" from the list of devices your cell phone discovers.
When your cell phone asks for an access or authorization key, enter "1234."
Check that your cell phone confirms the pairing. Your receiver is now ready to start making hands-free calls via your cell phone.
