Using the SATA slot as opposed to the other IDE was an idea for two people who wanted to burn two discs at once with more speed than usual. The diagram here
should show you where things need to be, (it's the right angled connector with the pink flash on it-next to where it says ODD SATA).
If you do choose to fit one, get a small phillips screwdriver and a 300mm at least right angled to flat SATA lead, then you'll need to;
First get an IDE to SATA power adaptor lead. You'll need it to plug the original power lead into.
Then, remove the fans and memory cover, or as much as you need so you can get your hands in comfortably.
plug the right angled end into the mother board an thread the rest of the cable up behind the drive caddies………
The rest should be self explanatory.