To apply BIMI to a specific subdomain, you must create a separate DNS TXT record directly within that subdomain's DNS settings. The record should follow the format `default._bimi.subdomain.example.com` and point to the SVG logo file. Given that BIMI typically trickles down from the apex domain, this subdomain-specific record ensures it only applies to the intended subdomain. Additionally, the subdomain should have a properly enforced DMARC policy (p=quarantine or p=reject), as well as valid SPF, DKIM, and, in some cases, SSL certificates for the logo to display correctly, enabling granular branding control across different subdomains.