Log in to your GoDaddy Domain Control Center.
Select your domain to access the Domain Settings page.
Under Additional Settings, select Manage DNS.
Select ADD below the table of your existing DNS records.
Choose TXT from the record options drop down menu.
Enter the details for your TXT record:
Host: Enter the host name for the TXT record. For example, Type @ for an SPF record, or enter the value _dmarc for a DMARC record.
TXT Value: The value you are setting as the destination of the Host.
TTL: Determine how long the server should cache information.
Select Save to complete your updates.
Create a free OnDMARC account to test your configuration.