sudo add-apt-repository ppa:certbot/certbot
sudo apt-get update
sudo apt-get install python-certbot-apache
Best to install all subdomains along with root domain
sudo certbot --apache -d example.com -d www.example.com
Note this will cause apache errors, as references to the cart are not removed. Best to a2dissite the site first.
certbot delete
sudo apt-get ssl-cert-check
su root
cd /etc/letsencrypt/live
ssl-cert-check <my_domain>/cert.pem