Cloudbric can protect the main domain (www.domain.com) as well as the subdomain (subdomain.domain.com). Cloudbric protects your website by subdomain unit. So all the subdomains you want protected should be added manually by clicking the 'Add site' button.
If you registered your domain using the name server method, make sure that you have added your subdomain at https://www.cloudbric.com/console/settings/dns with your original IP address.
Then, all you need to do is register your subdomain by clicking on the 'Add Site' button.
If you registered your domain using the a-record/cname method, all you need to do is register your subdomain, then change your subdomain's DNS records with the ones provided by Cloudbric.
Sometimes, a subdomain may not be in the DNS records of your domain provider. Then you must add the original DNS records at your domain provider first, then register your site at Cloudbric.
Read more about protecting subdomains here.