To enable SSL in Magento, go to System > Configuration
Click on “Web” link on left menu.
On this page, set Auto-redirect to Base URL to No.
Under “Unsecure” option, change the URL to use HTTPS.
Under “Secure” option, set “https” for Base URL. Set “Yes” for both “Use Secure URLs in Frontend” and “Use Secure URLs in Admin”.
If your Home page is linking to non HTTPS link, this is because Default page is set to CMS page, you need to edit and replace content of CMS page to use HTTPS links under Magento Admin > CMS > Pages.