From the top menu bar, select Domain, My Domains, click Manage Domain.
Choose Nameserver from Menu Tab, add below nameserver.
Click Change Nameservers to save the setting.
Second Method: Using the domain management panel (Note: domain have subscript the DNS management service and pointed to domain registrar DNS)
Once get the IP, login to client area, from the top menu bar, select Domain, My Domains, click Manage Domain.
Choose Management Tools and select Manage DNS from drop down menu.
After that, follow below image to add the IP as 'A' record.
Click "Save Change" to save the setting.