Speakers connected to sound card but no audio

Hello,

I have the Logitech Z333 2.1 speakers and a creative xi fi titanium hd sound card.

The speakers work by having the satellites connect to the subwoofer and then the subwoofer connect to the PC(3.5mm). Due to this I can't seem to connect it to my soundcard(Ive tried female 3.5mm to L/R RCA male but no audio).

What I was thinking was that since my subwoofer has L/R output(3.5mm) and L/R input(RCA) would it work if I connected from my PC, L/R RCA to the subwoofer and then from the same subwoofer back to my speakers.

Thank you very much and I apologise if the question is stupid or my explanations are bad, I am quite illiterate in these things.