(https://i.ibb.co/5FYpyR8/Screenshot-at-2023-10-02-20-17-08.png)
Well I doubt you have access to the centos-webpanel.com domain name.
Your server has to have a FQDN, pointing to the base IPv4 as mentioned in the documentation.
And then you can follow this Wiki to create a SSL for it:
http://wiki.centos-webpanel.com/hostname-ssl-with-letsencrypt