NFS/Samba external storage setup

New to NextCloud. Installed version 16.0.5 on a Raspberry Pi 3B. Have an USB drive for external storage.

Thought I could use NextCloud as a NAS via Samba or NFS. Ideally not a share open to writing by any system, but by login.

Have not been able to create an External Storage. The red exclamation point does not provide detail as to what needs to be changed.

Do not understand how to go from nc-datadir to External storages. First was fine, stuck on the second.