From AMA post:
To set up a new domain, you need a service called a domain registrar. There are many of these available, but some popular ones include Google Domains, Domain.com, and Namecheap.com.
Most registration services cost money, but it can be quite low for domains without a lot of competition (a couple of dollars per month). You’ll have to check on a specific domain name to get an accurate answer.
-GH Greg