Open the pending certificate and press Configure now. Three things happen on this page:
1. The CSR. A certificate signing request carries the domain name (the Common name) and, on multi-domain certificates, the additional names (SANs). Paste one from your server if you have it - the page decodes it so you can check what it says - or let the page generate it. The Common name must be exactly the domain the certificate is for.
2. Contact details - the administrative contact the authority records.
3. The validation method - how the authority checks the domain is yours:
- Email - a message to an address on the domain; click its link.
- DNS - add the CNAME record the page shows to the domain's DNS.
- HTTP - place the file the page provides at the path it names on your site.
After validation the authority issues the certificate and it lands on the certificate's page, ready to install. If validation stalls, the page shows which method it is waiting on - the DNS record or file it expects is spelled out there.