To begin the physical factory reset process you will need to remove the NVR cover. Use a Phillips head screwdriver to remove the screws on the casing. Once the screws have been removed, remove the lid to expose the NVR's motherboard.
On the motherboard you will notice a small reset button. This is the factory reset switch for your device:
To factory reset the device, hold the reset button down and unplug the NVR from power. Once power is removed from the unit, continue holding the factory reset switch for 4 - 5 seconds, continue holding the reset switch and plug the power supply back into the unit. You should hear a beep if not that is alright. Continue holding the reset switch and allow the device to initialize for 20 - 30 seconds and then release the switch once the system finishes loading.
When complete the NVR will be reset to its original factory settings allowing you to initialize the device.