WordPress do not accept my domain

I have bought the domain https://www.getobiasdeaguiar.com.br for my wordpress website getobiasdeaguiar.wordpress.com, when I try to add this domain it says that I cannot do it, so when I try to change the WordPress DNS gives me an error that I cannot do it this change.

The problem is this site – https://www.registro.br that does not recognize the DNS of WordPress. The site said the DNS server is refusing to send the domain information to its system.
I receive an email from registro.br which says :
the DNS domain server must be previously configured for the domain you want then you can register your domain with .br

Where can I configure this in the WordPress if it accept this operation just after registering the domain?