It would help us help you if you can be more specific than “it says I need to do DNS registration or something.” For example, you could quote from the docs to more specifically tell us where they started not making sense for you.
As it is, my best guess is that you don’t know what DNS registration is? If so, know that that’s not an Anvil-specific topic. It’s something you can Google and there will be helpful info elsewhere. But, basically, you need to purchase a domain name from a domain name registrar (like GoDaddy). Then you’ll be able to login to an admin panel with that registrar to setup the DNS records you need.