You need to read up on glue records, first. I think that’s the biggest piece you’re missing in your understanding. Some registrars call them “name servers”, which is true, but they’re the records that go into the root top-level domain name servers, which you can’t directly control. You have to create records with your registrar and they get pushed to the root name servers…then they delegate name service to your domain to your name servers.
Some registrars require your name servers to be resolvable by name, while some allow entering names and IPs, which allows kickstarting a zone from nothing. In the former case, you’ll need to first create A records for one of your domains in your registrar’s DNS (or on some other DNS servers that already have A records that resolve), and use those for your glue records until your zone is live and you can move all the records over to it.