Configure your Domain Registrar (other)
Setting up WHMCS with domain registration is simple and increases your revenue.
First, navigate to Configuration > System Settings > Domain Registrars (Setup > Products/Services > Domain Registrars in WHMCS 7.10 and earlier).
Click the Activate button for the registrar you wish to use.
The page will reload. Enter the information to authenticate with the registrar's system.
Then, click Save Changes.