Adding a Sub-Domain to an Existing Website (subdomain.yoursitedomain.com) You can add a sub-domain to your existing website, such as subdomain.yoursitedomain.com, to help organize a large or complex site into multiple smaller sites. For example, if you have a members only section of your website, you may want to consider adding a sub-domain called members.yoursitedomain.com which has the members...