Reply to HELP! 2.1 Speakers + Sub ????

Hey all! My vestax spin arrived today but I have run into some troubles

I cant get my speaker system to work with it, Basically my Sub box has an input where my speakers Red/White cables go and then the sub box has a standard cable for PC/Mac audio input.

I tried putting my Red/White cables in the Spin on their own but they were very tinny and quiet.
How to I use my (Powered) Sub box + 2 speakers to work with my vestax spin??
Thanks, Just ask if you need photos coz I dont believe I described it very well lol