Add the domain
Open Settings → Custom domain, enter your domain, and save.
DNS
For a subdomain such as forum.example.com, add:
forum.example.com A 101.33.68.124
or a CNAME to your site subdomain. Use DNS only first if your DNS provider proxies traffic before the origin certificate is ready.
Verify
Click Verify DNS. A TXT record may be required for ownership. Once verified, Caddy issues HTTPS automatically on the first request.
Renewal
ACME certificates renew automatically. Uploaded certificates are tracked in Settings → Certificate plan and must be replaced before expiry.