If you have IRC server and you are connecting with the IP ex: /server 122.12.12.12 but you want to use hostname, like /server irc.myserver.com, you need to register the domain myserver.com, or any other domain you like and it is not registered by someone else.
Once you register domain, you need to add A record in the DNS settings or whatever your domain register uses to control those settings, below we will show how that looks like using Cloudflare panel.
So irc.myserver.com should point to 122.12.12.12 and DNS of 122.12.12.12 should point to irc.myserver.com.
