The standard spec for your machine has one DVD R/W as fitted. Can you confirm that theer are two drive bays at the top of your tower and that one is empty? (The eject button should only work on one). If so then you can fit another DVD in here.
The cabling should be already available inside the box when you open it. One will be a power cable and one an IDE data cable.
click here for guide to fitting.
Note point about second drive and need to set jumpers on drives to master and slave.