Creating Your CNAME Record
During the set-up of your custom brand, you will need to create the Subdomain for your site and a CNAME Record for the subdomain. This is an action that occurs in your DNS Records, so please work with your IT provider to accomplish this action.
A CNAME, or Canonical Name, record is an entry within the Domain Name System (DNS) that specifies where a user can find your web pages, or any other URL. You'll use this to associate your custom domain with your site.
After registering your domain, decide if you want to use a particular subdomain for your site. E.g. instead of www.mydomain.com you could use something like uploads.mydomain.com, if you want. Then you'll create a corresponding CNAME record for that address. Keep in mind that changes to DNS records make take up to 48 hours to take effect.
Each hosting service has slightly different ways to create CNAME records. Guidelines are provided here for some of the common services. When in doubt, check with the particular company you're using for additional help or instructions.
If you manage your DNS records through your registrar, here are links to some step-by-step instructions to some of the main registrars that will help you with this action.