Hi and welcome to the forum! You can only use our subdomains on free hosting, exceptionally on Premium Hosting if you ask their support team on a ticket to migrate your free hosting account, then nowhere else. If you want a domain you can use on a DNS provider like Cloudflare, you can get one from EU.org; here’s a guide:
Afterwards you can port map your PC to the outside Internet through your modem’s settings and install everything you need for the web server on your PC. If you still need a domain quickly and DNS management without external nameservers, you can try using the alternative on the post I did some months ago: