The SSL page under your client area lists your certificates and sells new ones - these are paid certificates issued by a certificate authority, the kind that carries organisation validation or warranty where the product includes it.
Ordering is like any product: pick the certificate, pay the invoice. The new certificate then appears under My certificates as Pending configuration - it exists as an order, and the next article's configuration step is what turns it into an issued certificate.
Certificates have their own expiry, shown on each one's page. Renewal is a fresh invoice ahead of the date, like a domain.