Check if your car's audio has bluetooth. If so, you should be able to set it up to play over that. If not, your easiest options are either a USB to FM transmitter or a USB to AUX ditto. A USB to FM transmitter is a device that plays back music and transit it over an FM frequency of your choice. You'll just have to find a frequency without an active radio channel playing. You can find plenty variations of them on Amazon. Look up their sound quality before you buy, as they do convert digital to analogue radio which means they can affect the sound quality quite a lot.