Process done as ROOT user.

NOTICE: For CentOS servers replace apt-get with yum and replace apache2 with httpd

Installing git & Let’s Encrypt
Let’s Encrypt is a new Certificate Authority:
It’s free, automated, and open.

Check to make sure mod_ssl is installed:
On Sentora Panel go to Admin -> PHPinfo -> View Full PHP Configuration -> Search for mod_ssl
If not, install it:
NOTICE: For CentOS replace apt-get with yum
Code:
apt-get install mod_ssl

Check to make sure openssl is installed:  (openssl does not mandate the install of mod_ssl in CentOS 6.x)
On Sentora Panel go to Admin -> PHPinfo -> View Full PHP Configuration -> Search for openssl
If not, install it:
NOTICE: For CentOS replace apt-get with yum
Code:
apt-get install openssl

REQUIRED for CentOS: Edit /etc/httpd/conf.d/ssl.conf and change Listen 443 to #Listen 443

Next, install git and Let's Encrypt:
NOTICE: For CentOS replace apt-get with yum
apt-get install git
git clone https://github.com/letsencrypt/letsencrypt
cd letsencrypt
./letsencrypt-auto --help

Creating a Certificate for your domain
You need to turn off apache before creating a certificate or you will get something like
 

The program httpd (process ID XXXX) is already listening on TCP port 80. This will prevent us from binding to that port. Please stop the httpd program temporarily and then try again.
 

REMINDER: Replace domain.com by your domain URL.
NOTICE: For CentOS replace apache2 with httpd
service apache2 stop
./letsencrypt-auto certonly --standalone -d domain.com -d www.domain.com
service apache2 start

Changing Sentora port:
On Sentora Panel go to Admin -> Module Admin -> Apache Config > Override a Virtualhost [Select VHost] ->
Tick Port Override.
Forward Port 80 to Overriden Port: 443
Custom Entry:

(Don't forget to replace domain.com with your domain's URL below:)
 

Save Vhost.

Wait on daemon update or run it manually and restart apache.
NOTICE: For CentOS replace apache2 with httpd
php -q /etc/sentora/panel/bin/daemon.php
service apache2 restart

Your domain should now be secured by SSL.
You can test it here: https://www.ssllabs.com/ssltest/