Well, if you mixer is also functioning as a full external audio interface, you'd just connect it via USB (or maybe FireWire), make sure the correct drivers are installed and then you can basically use it as your sound card. You'd just have to go into the program/audio driver settings of Music Studio and configure this as your (ASIO) device.

If you were just using an analog device or if you can only make use of the analog connection on this device, you'd have to connect it to the line in socket of your actual sound card.

I hope this helps.