For some reason they do not have the picture of a MacPro. AnyWay: The drive is easy to put in. When you get your IDE optical 5.25 drive, you will take the drive door off the drive. Then you shutdown and open your MacPro side door. Make sure the door lock on the back is fully up. Pull the optical bay try outwards. It should slide right out. You can tilt it to remove the cables on the top drive and then pull it the rest of the way out. Install the lower drive you prepared and fasten in with the screws mounted on the drive mount. If none use the screws that came with drive. Place the drive tray back near the opening and attach the cables, including power. Slide the tray back in until it seats. Put the side panel back on and lock the latch in back. Boot up. There will be a new item on your menu bar to the left that you can use to eject the top and bottom tray.
If you need to load software for the new drive it is better loaded before you start the install. Piece of Cake.