How to Setup for Karaoke

First of all thanks for helping. Just bought a MG12XU, it came with a licensed copy of Cubase AI 8.
Mic is connected to Channel 1.
two speaker L/R connected.
USB driver is installed in laptop and USB is connected. When I play something in my laptop it does come out in the speakers

I have few karaoke tracks online which I wish to play, sing through the mic and record it in laptop. I have read and tried many things but I am not able to record anything in my laptop.

perhaps I don’t understand how to setup the switches in mixer and settings in Cubase. Can someone please help me step by step how to send input from laptop and capture the output from mixer in the laptop using USB