I have set up a user folder for my sister on my ‘My Cloud 4100’. She has created an account on mycloud.com but there are only instructions to look for the NAS when it is on the same network. She is using a desktop PC at her home, not a mobile device but I have sent a code to register a new device.
I’m sure there used to be piece of software to do this but it doesn’t seem to be available any more.