Run the container typing -p option before the image name
docker run --name rva-db -e POSTGRES_PASSWORD=rva -e POSTGRES_DB=rva-db -d -p 5432:5432 postgres
As for Docker run reference docker run has this format
docker run [OPTIONS] IMAGE[:TAG|@DIGEST] [COMMAND] [ARG...]
Options must be before image name. After that you can set entrypoint or command (when theyy differ from default from Dockerfile) and their arguments.