If you've been following along with my series you may find after tackling the motherboard and all its intricacies this step should be breath of fresh air.
Choose which drive bay you want to install the drive to and remove the face plate off of that bay. It's not really important which bay you use. I generally place it lower on the case face because that's where it's always been for me. If you're installing a zip or CD/DVD drive simply pick the bay you wish. I have both a floppy and CD/DVD drive as I use both mediums to transport data.
Do you know why it's called a floppy?
It is called floppy because it flops if you wave it. Seriously, do you remember the old 5 ? disks and how if you flailed them around they would almost bend double.
Now, slide the drive into the bay from the front. If your particular case has a drive rack, then you may need to remove the rack from the system and then screw the drive into the rack separately from the actual case. Otherwise, screw the drive into the case itself. Before doing so, make sure the front of the drive is flush with the front of the PC.
If you are using brackets to hold the drive in place, secure them now. You may need to temporarily disconnect the cables. Once in, tighten the drive in place. Double-check the connections, also checking the connections for other drives to make sure you didn't bump one out of place.
This wasn't necessarily the hardest step, but in my humble opinion this particular piece of computer hardware is vital. Try loading a new operating system or a needed document without either drive.