There is tethering a camera to a computer system and there is using a mobile using NFC connections which requires a bluetooth feature on the camera.
None of the Nikon D3xxx series cameras can be tethered using Lightroom CC. Your friend would either need to upgrade to a D5xxx series camera or purchase the WU-1a Wireless Mobile Adapter ($60). If they want to use their mobile, straight away, then they would need to consider the newest Nikon bodies which support bluetooth
For more information, I suggest that you call the Nikon Helpline 800.NIKON-UX