C3 Numark Mixer

[Roy Dennis]

That mixer does not have a built in amplifier.
You are confusing me a bit now. When I answered your previous question I assumed you already had the mixer. You either have to have speakers that have their own built in amplifier which the active implies or you need an amplifier between it and none powered speakers.
When you said your computer speakers I again assumed you have a separate set of speakers that you plug into your laptop, these are normally powered (Active) speakers with their own small amplifiers built in. I would not normally think of these as powerful enough to use for a karaoke party but OK for you to sing along and practice.
They won't be any more powerful coming from the mixer than they are from the computer itself so if you find them loud enough then OK.
Regarding the woofer, if it is complete system with the 2 satellite speakers then that probably contains the amplifier part so you would plug this into your laptop or mixer then the satellite speakers from that.
It's a job to answer you properly because I don't now the setup with the speakers.