Think he is meaning how to turn on the Air Con as on a lot of cars you have an A/C button to turn the A/C on or off.
In the A4 with the climate control the A/C is on all the time depending on what temp you have the cabin set to. For example if you set your temp to 18 and the cabin is 21 when it will put the air con on to cool the cabin down to the desired temperature. To turn off A/C so i doesn't come on with the climate control press the ECON button, that will turn the A/C compressor off