The product showing here is model FMP04B, all other HYSTOU fanless mini pcs using the same guide shows here.
Step 1. Get the mini pc, extra HDD, SATA cables and screwdrivers ready.
Step 2. remove 4 screws and open the case from bottom side.
Step 3. Plug the SATA Data cable to SATA port onboard, and plug the SATA power cable to power plug onboard
Step 4. Plug the other side of SATA cable to HDD Power and Data plug, now we already connect HDD to the mini pc, next we only need to fix the HDD onto bottom case.
Step 5. Fix the HDD to the bottom case, match the HDD screw holes to the case Screw holes.
Step 6. Fix the screws for HDD, and then fix the screw for bottom case and now work finished.