via EuroDNS control panel
Log in to your EuroDNS account, click on Control Panel.
Click on Name Server Profiles under the Domain dropdown menu. Now you can create new name server profiles or edit existing ones.
If you’d like a default profile, click on the green tick next to the profile name. The tick is highlighted if the profile is set as default.
via WHMCS admin panel
Log in to your WHMCS admin panel. Click on the column Setup and select General Settings.
Click on the Domain dropdown menu. You can choose to enter a default name server in the middle of the page.
These settings will apply to all your domain name registrations. If you need to change them, you can do it in either panel. To avoid a conflict when registering domain names, you must select the same default name server in both the EuroDNS and WHMCS control panels.