A Secure Sockets Layer (SSL) certificate is a must for every online shop. It secures the communication between the client and the server ensuring that all sensitive data goes through a secure, encrypted connection (HTTPS).
In order to use an SSL certificate for your store, you should first purchase one. HostKnox customers can purchase a private SSL certificate from the HostKnox Client Area. The SSL installation is free.
To enable SSL in Magento, log in to the Magento admin panel and go to System > Configuration. From the menu on the left click Web and then from the options on the main screen click Secure.
In the Base URL field type the secure URL for your store, e.g. https://www.yourdomain.com/store/. Make sure you type https instead of http and end the URL with a slash (/).
Finally, you should set the Use Secure URLs in Frontend option to Yes. If you want to enable SSL for your admin panel as well, set Use Secure URLs in Admin to Yes. Click Save Config to save the changes and enable SSL for your store.
Note that SSL will not be enabled for your entire store but only for the sections where sensitive data is transmitted. This is so because secure connections (HTTPS) are slower than regular connections (HTTP), hence SSL is applied only where it is really needed.