When you add your site to Incapsula you get a CNAME for your subdomains (www.example.com, blog.example.com) and an IP address for your top level domain (example.com). You will be instructed to replace your exiting DNS entries for those domains with the entries you received from Incapsula. In order to make these changes, all you need to do is log into your DNS management console. If you are using one of the popular DNS management services (GoDaddy, 1&1 Hosting, etc.), we have prepared step by step instructions on how to make the necessary changes.