I think you have to setup samba share at your router first.
Or you plug in the hdd to your kodi device (if you have one like a raspberry).
Thanks for the reply but while i was waiting i couln't leave it alone so i managed to work it out on my own.
I connected the external hdd to my Asus media player with Le installed and used zeroconf-browser to find the LibreElec (SAMBA) connection and then everything worked fine.
But i wonder now, how does SAMBA-share setup in the router work?