aaaa record AKA quad record is the ipv6 address of your host server
go to your registrar, DNS record and put the ipv6 address you got from your host when you got the webhost server.
you don't need to fill in the site URL just leave it blank because that URL is the default.
after some hours it should activate. check if your site has an ipv6 aaaa record :https://ipv6-test.com/validate.php