PowerSpec G464; Two questions: 1) How to add an HD, 2) Issue using one HD on the RAID controller.

From the front, you want to remove the right side cover. You'll be able to access the area under the piece that hides the power supply. There will be a 3.5" bay there to add drives. Regarding the Silicon Image 3114 RAID controller, that sounds like it's referencing another system from a while ago. This is an X570 board, it's an AMD Storage controller using RAID Xpert2. It supports RAID 0, 1, 10. You shouldn't have any issues setting up RAID.

There's no need for RAID if you're adding one additional data drive. RAID 0 is a striped array, adding two drives together into one. These would be ideally identical drives. For instance if you had two 4TB drives, that you wanted to act as a single 8TB drive. However, RAID 0  has little in the way of data redundancy, it's not a good idea on a data drive. Also, HDD's are slow, RAID 0 will come nowhere near making up in comparison to SSD's.

Second options is RAID 1, a mirrored array. You add two, one drive is an exact mirror of the second. This is done in real time, so you again prefer two identical drive. It's not required, but if you mirror a 1TB and a 2TB drive, you'll effectively have a single 1TB drive for storage.

RAID 10 is actually 0+1. So four drives, striped and mirrored. As an example 4x1TB. You would see a single 2TB drive as storage, but the array is backed up by two additional drives.

If you're adding just a single data drive, all you need to do is connect it. You'll need the screws, 6-32 UNC x4, and the SATA cable. Once you connect it, it'll show up. if it's a brand new drive, you'll need to initialize and partition it. That's all that's required.