I just finished doing everything in that Wiki tut, but the last part has me a bit confused. Looks like it has two different names. Bolded the pat I'm questioning. As For the content I bolded what I think the file would look like once created.
Then you can extend the systemd service by creating the following file:
@jonathon thanks for the help. Took the chance that I was right that the one part was folder and file name so created folder emby-server.service.d with file write-permissions.conf with that ciontent in it then that to a user this morning on the Emby forums ran sudo systemctl daemon-reload and sudo systemctl restart emby-server, was told to run another command by console, ran it, checked Emby and all is working perfectly now. Thanks again for the help with this. I honestly would of never found that Wiki you linked to.