From the web, go to the particular camera you want to delete and select the link “Unregister camera”
Once selected, it will typically take 1-3 minutes for your camera to fully reset itself back to factory settings including deleting all of the previously stored video footage. You’ll know when the camera has finished resetting itself when the LED's are flashing blue. See more on LED states here.
IMPORTANT - if your camera has not fully reset itself before you unplug it, you might have difficulty re-registering the camera the next time you plug it in. If this is the case, you should plug the camera into ethernet first and wait until the LED's give the indication that it is ready to be re-registered.