Hi how can I work aux input.I did everything but doesn’t work.Thx

People, people, people. Okay there are many thousands of devices out there and they are all different. I need to know what brand and model stereo your talking about. Typically though the AUX on most stereo's is on the front face plate of the unit (some are on the back side of the unit though) consists of a 3.5mm (walkman style headphone type jack where you can plug your input device into your car stereo via a Male to Male 3.5mm stereo headphone cable. (avail at walmart, etc) Once you've done that you cue up your device and start playing it at half volume. Dont turn volume all the way up use stereo volume to dial it up. Dont want volume to max going into your stereo plus your stereos amp. It's possible distortion overload city there. Then on the stereo itself there should be a button for inputs you push that button until you select AUX and walla. Also some stereos in there settings they have a special selection for gain control for AUX which allows you to find that happy medium for the stereo to boost the music from AUX properly. Ideally it would be a line out (not volume controlled just a straight signal) but most devices only have headphone out which incorporates it's own little amplifier in there and too much volume aka signal current going into the amp is not good for it.