Install SSL Certificate on Apache for Debian

Prerequisites
OpenSSL installed and updated (should be installed by default)

apt-get update 

apt-get upgrade openssl

Apache will be our HTTPS server. To install it, run the following:

apt-get install apache2

Enable the Apache SSL module

a2enmod ssl

The default Apache website comes with a useful template for enabling SSL, so we will activate the default website now

a2ensite default-ssl

Configure Apache to Use SSL

Edit server configuration file

nano /etc/apache2/sites-enabled/default-ssl.conf

Locate the section that begins with <VirtualHost _default_:443>.
Add a line with your server name directy below the ServerAdmin email line. This can be your domain name or IP address:

ServerAdmin webmaster@localhost 

ServerName example.com:443

Find the following two lines, and update the paths to match the locations of the certificate and key. If you purchased a certificate or generated your certificate elsewhere, make sure the paths here match the actual locations of your certificate and key:

SSLCertificateFile /etc/apache2/ssl/apache.crt 

SSLCertificateKeyFile /etc/apache2/ssl/apache.key

Restart Apache to put these changes into effect

service apache2 restart