Force all of your pages to use HTTPS. To do this you will need to modify your .htaccess file.
Using the Code Editor in the File Manager, add these lines to the beginning of the .htaccess file.
RewriteEngine On
RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*)$ https://mydomain.com/$1 [R=301,L]
Change "mydomain.com" with yours.