You can permanently migrate HTTP traffic to HTTPS by adding the following code at the top of .htaccess file on your website running by Apache or LiteSpeed:
RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
If you don't manage to do it, please open a support ticket and we'll do it for you.
Update:
On cPanel v80+ you can force SSL redirection from cPanel > Domains interface.
Set Force HTTPS redirection to ON
