To set up a DMARC record, you need to add a TXT record to your DNS settings. Here is an example:
_dmarc.example.com IN TXT "v=DMARC1; p=none; rua=mailto:dmarc-reports@example.com"
In this example, 'v=DMARC1' denotes the version of DMARC, 'p=none' specifies the policy (none, quarantine, or reject), and 'rua=' specifies the email address for aggregate reports.