Just plug the optimum into the car cigarette lighter, tune the car radio to the same frequency (range from 87.5 to 108 MHz). Then let your phone/audio player pair it via Bluetooth/USB flash driver. 2 PORTS USB CAR CHARGER: Comes with 5V-2.4A and 5V-1A charging ports which output 3.4A total, support charging two devices simultaneously, better-charging performance! ANSWER CALLS HANDS-FREE: High-performance microphone with Noise Suppression (CVC) technology, grants you crystal clear call. Answering/redialing/dismissing or ending a call just simply click a button. Seamlessly switches between incoming calls and music; Drive more safely. Insert a USB flash drive which contains MP3 files into the "RIGHT" USB port and enjoys it. If that's not enough, it can also support your playlist with a full range of audible frequencies Stream music and calls directly from your mobile devices to car stereo system via FM radio signal ( 87.5-108.0 MHz). Specification: version: JL2.1 Protocol: AVRCP, HFP, A2DP Screen Display: Yellow LED digital display Frequency range: 87.5-108.0MHz Frequency stability : 10ppml Product Input: 12-24V Charger output: 5V/3.4A Music Format: MP3, WMA Mic: 4.0MM*1.5MM USB(Max capacity): 32GB FM Transmit Distance: about 5 m Product Weight: 34g Product Dimensions: L78*Diameter 35mm Material: ABS Package Includes: 1x with Dual USB Charge Port 1x User