Log in to your GoDaddy account and go to the "My Products" page.
Click on the "DNS" button next to the domain for which you want to configure DKIM.
Scroll down to the "TXT (Text)" section and click on the "Add" button to add a new TXT record.
In the "Host" field, enter the name of the subdomain you want to use for DKIM, such as "default._domainkey".
In the "TXT Value" field, enter the DKIM key for your domain. The key is typically provided by your email provider or can be generated using a DKIM generator tool.
Save the changes by clicking on the "Save" button.
Wait for the changes to propagate, which can take up to 48 hours.
Once the changes have propagated, you can check if your DKIM record is properly configured by sending an email from your domain to a Gmail or Yahoo account and then checking the email headers. Look for a "DKIM-Signature" header in the email, which indicates that the DKIM record is properly configured.