You can force your website (all pages) to use http or https by modifying your .htaccess file.

Just insert below small lines to the beginning of the .htaccess file.

RewriteEngine On
RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*)$ https://yourdomain.com/$1 [R=301,L]

[Change yourdomain.com to your real domain name]