Set a custom TRAEFIK DEFAULT CERT when using docker compose

I am using traefik as a proxy inside a docker container and would like to set my own custom default cert(it is not generated by letsencrypt). I read the documentation at https tls docs and it seems I need to edit the config file. I tried locating the config file inside the container but I can't to find it searching traefik just gives me the location of the binary.
I wonder if there is an easier way to do it when using docker compose. I am using the traefik:2.5 docker image. Thank you.

Why would you use an outdated Traefik version, when current is v2.10 ?

You can declare a default TLS cert in a dynamic config file, which you need to load with provider.file in static config. (Doc)