Transferring an Existing SSL Certificate
If you already have a security certificate for your domain, it can be easily transferred to your Magento Go store. If the process was managed by your service provider, you may not be familiar with the files involved. The files you need are summarized at the bottom of this topic.
Magento charges a $99 annual fee for any SSL certificate that is purchased or transferred from a third-party provider. The fee includes installation on the Magento Go server and a dedicated IP address, and is in addition to any fee charged by the third-party provider. To learn more, see: Secure Your Online Store with its Own SSL Certificate - Pricing.
Add Custom SSL
Step 1: Get the Certificate Files
Step 2: Upload the Zipped Certificate Files
Step 3: Update Your DNS Settings