This is actually one of the easier upgrades/additions you can perform. All you need to do is install the SATA hard drive in the case, giving it a data cable and a power cable. You might want to check if you have a spare data cable, or else you'll need to get one with your hard drive (if it isn't included).
Once you boot up with the new drive installed, just go into Disk Management, and you'll see the new, unformatted drive. You may get prompted to initialize the disk...at which point the default MBR option is what you'd want. Then you can right click on the drive, create a partition, typically the full size of the drive, and the wizard will work you through the steps, including giving it a drive letter and a volume name.