Move the tempered hardboard panels to the room you are installing them in and lean them up against the wall vertically. Leave the panels in the location for 48 hours before installation so they can acclimate.
Stack the panels up in a pile to provide space to work. Measure the height of one wall. Don safety goggles and cut the tempered hardboard panels, if needed, using a circular saw and carbide-tipped saw blade.
Locate all wall studs with a stud finder tool and mark each location with a pencil. Make the marks on the ceiling or floor so you can locate them once the hardboard panels are in place.
Place the first hardboard panel up to the corner of the wall and locate a wall stud in the center of it. Insert 3/4-inch nails through the stud, spacing them every 8 inches. After attaching the panel to the center stud, insert additional nails through all remaining studs in the same manner.
Place a second hardboard panel beside the first so the edges touch but don't tightly butt together. Attach the second panel with nails in the same manner as the first.
Install all additional panels in the same manner until completing the room. Countersink all nails by placing a nail set tool over them and tapping the tool with the hammer.
Apply wood putty over the holes with a putty knife until they're flush with the panel surface. Wait until the putty dries and sand it smooth with 100-grit sandpaper.
Prime and paint the tempered hardboard with paint rollers as desired.