Running openvpn under mac

I have set up an openvpn server on a Linux machine (my-server) - I have tested it, it works well.

Someone who wants to join the VPN is running a mac (El Capitan) - I do not use macs. I do not have access to the machine (due to covid-19 problems amongst others).

The installation has created /usr/local/etc/openvpn/
He has unpacked a tar file there that contains my-server.conf that is the client config for my openvpn server. This references files by relative paths, eg:
my-server/keys/his-client.crt

It fails with messages like:
May 13 23:25:21 PetesG5 com.apple.xpc.launchd[1] (homebrew.mxcl.openvpn): Service only ran for 0 seconds. Pushing respawn out by 10 seconds.
May 13 23:25:31 PetesG5 com.apple.xpc.launchd[1] (homebrew.mxcl.openvpn[63178]): Service exited with abnormal code: 1

Where should we look to get more informative error messages ?

I suspect that the config files are in the wrong place, I cannot see anywhere in the documentation that says where they should be.

Thanks in advance