How to transfer domain to claudflare?

I have domains in 3-4 different registrars and I want to transfer all of them to cloudflare, but I dont see how.
There is no field like other registrars to fill the domain and authorization code.

4 Day I am looking for information how to transfer domain to claudflare but I cannot find. I found video in you tube and some info here in documentation but there show with some existing domains in list. How to do this.

Is it possible someone to show with screenshots of short video how to do this?

Are those domains already on Cloudflare plans? The do need to be, and need to use Cloudflare name servers while registered here.

Dont have plans. I dont want use plans.
Is Claudflare standard registrar or
I want use my DNS as every other registrar