To point a domain to HTTPS you need to add the path of the SSL certificates in the virtual host configuration file and
Step1: Open the example-zehncloud.com.conf file to edit.

sudo nano /etc/apache2/sites-available/example-zehncloud.com.conf

The default files look like:

    ServerAdmin admin@example-zehncloud.com
    ServerName example-zehncloud.com
    ServerAlias www.example-zehncloud.com
    DocumentRoot /var/www/html/example_zehncloudcom
    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined

Step 2: Add the following code:

ServerName example-zehncloud.com
ServerAlias www.example-zehncloud.com
DocumentRoot /var/www/html/example_zehncloudcom
Redirect permanent / https://example-zehncloud.com/



# The ServerName directive sets the request scheme, hostname and port that
# the server uses to identify itself. This is used when creating
# redirection URLs. In the context of virtual hosts, the ServerName
# specifies what hostname must appear in the request's Host: header to
# match this virtual host. For the default virtual host (this file) this
# value is not decisive as it is used as a last resort host regardless.
# However, you must set it for any further virtual host explicitly.
ServerAdmin webmaster@localhost
ServerName example-zehncloud.com
ServerAlias www.example-zehncloud.com
DocumentRoot /var/www/html/example_zehncloudcom
SSLEngine On
# Available loglevels: trace8, ..., trace1, debug, info, notice, warn,
# error, crit, alert, emerg.
# It is also possible to configure the loglevel for particular
# modules, e.g.
#LogLevel info ssl:warn
ErrorLog ${APACHE_LOG_DIR}/error.log
CustomLog ${APACHE_LOG_DIR}/access.log combined
# For most configuration files from conf-available/, which are
# enabled or disabled at a global level, it is possible to
# include a line for only one particular virtual host. For example the
# following line enables the CGI configuration for this host only
# after it has been globally disabled with "a2disconf".
#Include conf-available/serve-cgi-bin.conf
SSLCertificateFile 
SSLCertificateKeyFile 
SSLCACertificateFile 

With the port 80 for HTTP, we need to add another virtual host mapping to enable the service on port 443 (default SSL port). The virtual host mapping with the SSL i.e with port 443 requires SSL Certificate details.
The SSLCertificateFile points to the file with certificate data in PEM format.
The SSLCertificateKeyFile  This directive sets the all-in-one file where you can assemble the Certificates of Certification Authorities (CA) whose clients you deal with. These are used for Client Authentication.
The SSLCACertificateFile This directive points to the PEM-encoded private key file for the server. If the contained private key is encrypted, the passphrase dialog is forced at startup time.
Restart the Apache web server using the command

sudo service apache2 restart