Recording Karaoke from a Mixer

Hi, I’m new to the site and hope I am asking the correct things.
I have a Yamaha MG10XU mixer and want to record from the mixer onto my laptop some Karaoke songs with vocals.
Can some one advise me how to do this.
I can convert the MP4 tracks to MP3 if required.
I need to know how to put the vocals on to the MP3 tracks that I have placed on Audacity.
I need to get the sound of the vocals from the mixer as I am using a BOSS VE-20 Vocal Processor.

The usual way is to “overdub”. See: