multiple microphones

Hi.. Trying to get 2 microphones that will work with adobeconnect.  I have bought an "audiobox" usb, that takes 2 inputs.  Adobe connect lets me select "audiobox usb" as input, however, only the microphone hooked up to input #1 works, I'm trying to figure out a way to get both to work at the same time.  I am running it on a macbook air..  Both mic's have been tested and work.  Any help is greatly appreciated.  Thank you!

John