The following automates the process detailed here, in an earlier gist: https://gist.github.com/brunston/3c5b032f7a4c4882955f1c8985ca7fb1 You can enter the following commands in a bash shell. While I am not in the habit of providing nefarious bash scripts, it is always recommended to check the body of the bash script yourself before running on your server.
curl -o le-superauto.sh http://brunston.io/bash/le-superauto-ubuntu1604.sh
sudo ./le-superauto.sh <desired domain to issue cert to>
This bash script is supplied with no warranty, express or implied.