A common point of confusion that users make when first using a mixer are with the bussing assignments. First, make sure the channel is being bussed to the MAIN MIX.
At the very bottom of the mixer there are several buttons which can bus the audio to multiple locations. If you have a microphone for example connected to the channel one XLR mic pre input press the MAIN button there to send the signal to the main mix. This will also allow the audio to be sent out the USB output.
Also, make sure you have pressed the 2-TR/USB button on the SOURCE section. Also make sure that the 2-TR/USB to main button is not pressed down. This will ensure that the USB is being sent to the computer.
On a Mac it's not necessary to install any drivers.
On a PC:
Download the ASIO4ALL driver from the downloads section of your products webpage.
Find the link here:
You?ll need to record the audio into some kind of recording program of which Audacity is a good free open source program for Mac and PC to test with and can be found here: http://audacity.sourceforge.net/