Updating the list of DNS (nameservers) linked to your domain is a very simple operation and of course it is free of charge. Just login into your account and then click on the domain name you want to update. Then select “Update DNS List” and enter the two or more DNS (nameservers) you wish to link your domain to.
The list of nameservers is immediately updated, however because of the way the internet has been built, it can take up to 24 hours before all of the computers all around the world will accept and use your update. In most cases, any changes you make will be effective immediately.
Please refer to the following video tutorial for more details: