If your domain name is registered with Heartinternet, please follow these steps to update your nameservers:
Log into your Customer Area
Click on Manage Domain Names
Select your domain name from the drop-down list under Manage Web Hosting Domains
Click on Manage Now
Select Change Nameservers
In this section, enter the exact nameservers we've provided
Click Change Nameservers to save your changes
Your nameservers update will be processed within 3-6 hours. However, it may take up to 72 hours for it to be visible everywhere.