You can install Let's Encrypt certificates for your domains/subdomains/parked domains through the hosting Control Panel -> section SSL/HTTPS -> Let's Encrypt certificates. In this section, you should select the hostname for which you want to issue a Let's Encrypt certificate. If you want to have a certificate issued for all subdomains of a domain name, you should create a certificate for the * (wildcard) subdomain. Once you make your selection, press the button Enable. Doing this will automatically request certificates for the chosen hostname(s) and will have them installed on the server. If the selected hostname (domain/subdomain) is not pointed to our hosting service, you will not be able to issue and install a Let's Encrypt certificate for it. This is due to the specifics of the issuance of Let's Encrypt certificates. Attempts to issue a certificate for a hostname that does not point to our service will end as Failed.