If you want to be able to let other players or yourself run admin commands, you can simply list their names with these steps so the server will recognize them as admins.
Make sure that admins have made an account on Factorio.com and use their Factorio username. If you register with Steam, the name will be their Steam username.
1. Open the File Manager
2. Navigate to /config/
3. Right click a blank space and click New→File
4. Name the file server-adminlist.json
5. Right click the file and click Edit. Add each admin in this format:
6. When finished, Restart the server.