Login to your cPanel, scroll down and, navigate to lets Encrypt option. Click on issue license and your SSL will be installed within 5-10 min. After installing SSL you have to force it to https, otherwise, it may not fully secure.
to force https use this htaccess code and paste it to your htaccess file.
RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
If you use WordPress, you can install really simple SSL plugin to force SSL.
