In order to use this system you will need to obtain a domain name. There are many possible domain registrars and a domain name can often be obtained without much expense.
Your domain name will need to be one which you can obtain a TLS certificate for. This rules out many of the free subdomains available via some sites.
You will also need to have a dynamic DNS subscription set up. The most ideal way to do that is via configuring your internet router to handle it.