Logic Pro X Outputs

Hi,

I recently bought a Behringer X Air XR18 to use as an audio interface for Logic. I can get sound from all the tracks going into logic but how do I set up an output that will send to the aux outputs on the mixer as I have an in ear system that I connect to the sound desk and I want to be able to hear the sound inside logic along with the click through the in ears.

Thank you for your help,

Daniel.