Surround Sound 5.1 For Macbook

So I have these great Logitech speakers the z 530 I believe and they work amazing. I have all three plugs into the special adapter that came with it and from that I have an RCA cable connecting the red and white/yellow to my macbook. All speakers work perfectly and I know this might be a really stupid question but is that it? Do I have to somehow switch anything to make it set to 5.1 surround sound or is everything good to go? And is there anything that needs to be changed at all? It's not a big thing but I'm just really curious to know if I need to do anything to make it any better [which I doubt, it sounds AMAZING already]. If anyone has any questions or answers please get back to me! Thanks!

you need audio in 5.1

your stereo iTunes library isn't going to sound better in 5.1

I think DL meant to say you "don't" need 5.1 since it won't make a difference for iTunes. If your MacBook is capable of 5.1 you need this for other things:

Amazon.com: Toslink To Optical Mini Adapter: Electronics

I meant the audio you're trying to play needs to be in 5.1 if it's going to make a difference in surround sound.

I almost never see it around though, so I'm guessing it's still relatively rare, but you can get enhanced disks etc.