PC/laptop Connection to Mixer Desk

Hi, some help for tech ‘dummies’ please.

We have a Yamaha MG166CX USB Mixer Desk. We simply want to play music from a laptop or PC to the mixer desk and to the speakers and monitors. I downloaded the Steinberg USB Driver, and it added some software. Am I missing some more software? When we bought the desk around 2011 Cubase came with it but we never loaded it. This is the first time we have tried to use it with a pc or laptop.

We would very much appreciate some advice on how to get it to work, ie no sound. The OS is Windows 7. At the moment we have no sound unless we connect line in and then we can only hear it through the monitors.

Thank you