How to force SSL with .htaccess
If you want to force your entire website to go through https, you can add these rules to your .htaccess file:
RewriteEngine On
RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*)$ https://yourdomain.com/$1 [R,L]
from Siteground tutorial at https://www.siteground.com/kb/how-to-force-ssl-with-htaccess/