That is not a Dockerfile. That’s a manual for Dockerfile so you could run man Dockerfile on Linux to get some documentation.
When you got the error message, exactly which directory were you on the filesystem? I guess it was /usr/share/man/man5 because this is the case when you get the exact same error message that you quoted. Docker simply could not find any “Dockerfile”
“A properly configured config.yaml file must be mounted into the container during startup of the container.”
Do I put that config.yaml (which will be called /tmp/elastalert.yaml) into the actual container directory (/var/lib/docker/containers/d2c6f331b82481828f7daa9d12a4fab6132dc58a23675f2ef6eb460311baa2e9), or do I put it into /tmp ?
I am currently running that command without a config.
Please, read the documentation for that. Everything you need to know is in that. If you don’t understand the documentation after trying for some time, share how you tried and we can tell you what your mistake was.