How to use Let' S Encrypt well to have an HTTPS?

I use HASSIO on my raspberry 3, where Let’ S Encrypt creates the files? I do not find them.
here the order:
{
“challenge”: “https”,
“email”: “[email protected]”,
“domains”: [
xxxxt.ddns.net
],
“certfile”: “fullchain.pem”,
“keyfile”: “privkey.pem”
}

State always STOPPED !