While most registrars provide an interface where you can set your zone records yourself, your registrar should have a contact phone/email where you can request that they take care of it for you. See the previous article How Can I Use My Own Domain Name? for more information.
All registrar interfaces are different, which is why we recommend contacting your registrar for assistance when editing DNS records for your domain. Sample interfaces, with the correct configuration, are shown below:
Network Solutions-style interface