The private SSL certificate is an important upgrade to your website. The basic function of an SSL is to encrypt all communication between the browser and the server, ensuring that all data goes through a secure (HTTPS) connection. An SSL certificate is a necessity when you want to operate an online shop and process the sensitive customers data through your software. It helps you gain your clients' trust and increase your web site's search engines rank. You can purchase a private SSL from the SiteGround SSL Certificate page.
To configure Magento to work with your SSL certificate, first you need to login to your admin area and go to System -> Configuration.
Next, click on the Web link under the General tab in your left menu.
On this page, you will see many options that you can configure. However, focus only on the Secure tab. In it, make sure that you've set the Use Secure URLs in Frontend and Use Secure URLs in Admin to yes. Doing this will make your Magento application work with SSL for those parts of your site.
That's it, your Magento store is now configured to work over SSL!
原文：https://www.siteground.com/tutorials/magento/magento_ssl.htm