New MacBook Pro 13-inch audio input - how to get it working?

Hello!

Just yesterday I bought the MacBook Pro 13-inch model with i5 processor. Everywhere I look, i can see that the audio output is actually specified to be combined audio in / audio out.

When I plug in the headphones, in system preferences, audio output automatically turns to headphones. But when I plug in a 3,5 jack from my DJ Mixer, it still is only as headphones and input tab only has the internal microphone.

How can I get the input to work? Do I need a special adapter or something?

Thank you!