Assuming you have ssh on your main server (but not into the Discourse docker container), it should look like this:
Make sure that the ssl.crt file contains all of the certificates including any intermediate ones (see all the posts earlier in this topic for more on it)
And make sure that the permissions are set correctly. All I did was this to create the folders:
mkdir -p /var/discourse/shared/standalone/ssl
And then I put the files into that folder with the correct names.