Yes you would plug it into one of the short pcie slots. However if you don't have one (or your GPU is blocking it) you can also install the card into a full size PCIe slot (like for your GPU) and it will only utilize the pins it connects to.
A lot of people these days say don't waste your money on a sound card the onboard sound is just as good. And maybe when it comes to lower end cards thats true, but I am running a Sound Blaster X-FI Titanium HD that puts out sound that no onboard sound system can ever touch. And I've heard a lot of them, they are junk compared to a good higher end card. I run mine to a set of powered monitors and playing games on it is incredible.