FM transmitters are available in several different designs and models. A common option is a fairly small device that connects directly to the 12-volt socket in the car. Slightly more advanced models are mounted separately, for example, mounted on the sun visor and connected with a slightly longer cord to the 12-volt socket. Connecting your phone to the FM transmitter is easy. You find it as a Bluetooth device in the settings on your phone and connect to it. Then select a frequency for the FM transmitter to transmit on and tune it to your car stereo.