After the private name servers have been created, the necessary A records must be added to the primary domain. After the A record update, the private name servers will be available for use for your domain and for all of your hosted domains.
Once the name servers have been changed over to private name servers and A records have been added, there are no more steps that need to be taken. The process will be complete once the propagation period ends.
For more information on how to add an A record, please read the following knowledge base article:
If you don't know how to change your site's DNS or if your domain is registered with another company, please refer to our video tutorial section for more information.