The iTrip is a pretty simple device. The idea is that you plug one end into your car cigarette lighter socket and the other into the earphone jack of your MP3 player, replacing your car radio with the soothing sounds of your own music collection playing through FM radio.
It’s just that simple. Just plug it in and find a frequency where you hear only static. You’ll get better results if you find one that has some neighboring frequencies with static. Then use the + or – buttons to tune your MP3 player to the same frequency. Just like that your player has replaced your car radio.