jawad1234 webmin is a control software for a server (like a VPS). It helps you install and manage the tools needed to run a website, but it doesn't provide hosting or anything like that. The site you linked is their home page for the software, but like Flarum, it is software you must set up and use on your own server.
If you're unfamiliar on how to do that, I recommend you look at the webmin site and read their documentation to get an idea, and seek out their support if you have trouble setting it up. Then you can follow the official installation instructions.
