What to do:

1. Edit file /inc/header.inc.php

define('BX_DOL_URL_ROOT', 'https://domen.name/'); ///< site url    - Replace http to https

Save/Exit

2. Edit file .htaccess at the root of your site, default /public_html/.htaccess

After RewriteEngine on add

RewriteCond %{SERVER_PORT} !^443$
RewriteRule .* https://%{SERVER_NAME}%{REQUEST_URI} [R=301,L]

Save/Exit

All will be redirected to https