Insert the CD/DVD drives into the drive bays. Punch out the bay plates if you didnt earlier. Before tightening the screws make sure the IDE and power cables will actually reach...
Connect a power cable to each drive and an IDE cable to the second IDE channel [oops, no picture, see later pics]. The IDE cables are usually keyed so they only insert one way. Else, see the red stripe down the edge which denotes the Pin1 side. One of my IDE cables was a bit of a stretch, I should replace with a longer one.