Configure your configuration.php file

In you configuration.php find
public $live_site ='';
and replace with
public $live_site = 'https://www.your-domain.com';

Add the following code to the bottom of the .htaccess file

RewriteEngine On
RewriteCond %{HTTPS} OFF
RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}

Force SSL in your Joomla site

Admin Panel
click the Global Configuration button.

Server tab
Server Settings section, there are 3 Force SSL alternatives

None: SSL will not be enabled in your Joomla site.
Administrator Only: connections to your administrator will be on HTTPS.
Entire Site: connections all over your website will be on HTTPS.