There are two different reset operations that can be done with Ubiquiti devices:
Hard Reset
This resets the device back to its original factory firmware and settings.
Soft Reset
This resets the device's current (could be not the original) firmware's settings.
Hard Reset
Using a remote reset device:
Plug the ethernet cable of the reset device into the PoE port of the PSU.
Plug an ethernet cable into the wireless device but donot plug into the reset device.
Hold down the button on the remote reset device before plugging the cable that goes into the wireless device into the reset device.
Continue holding down the button on the remote reset until the Ubiquiti device has been reset:
The top 4 lights on the device flash in an alternating pattern of 1 & 3 and 2 & 4.
If the Ubiquiti device is not visible, use ping to find out when it has been reset:
ping 192.168.1.20
Release the remote reset device button, the Ubiquiti device has now been hard reset.
Alternatively, you can carefully press and hold the reset pin on the device until the top 4 lights start flashing in an alternating pattern of 1 & 3 and 2 & 4.