Once you have SSL certificate installed on your Nopcommerce site, there is a
setting in your Nopcommerce admin panel for you to force all your Nopcommerce
pages to be secured with SSL protection.
the instructions below to configure it.
1.Login to your nopcommerce site admin panel, click the configuration >> Settings >> General And Miscellaneous Settings.
2. Click the "Security settings", Check "Force SSL for all site pages".