How to register database in recovery catalog ?

[oracle@orcl ~]$

[oracle@orcl ~]$

[oracle@orcl ~]$ rman target / catalog  rcatowner/oracle_4U@demopdb1

Recovery Manager: Release 19.0.0.0.0 - Production on Sat May 24 15:07:56 2025

Version 19.3.0.0.0

Copyright (c) 1982, 2019, Oracle and/or its affiliates.  All rights reserved.

connected to target database: DB1 (DBID=1788905834)

connected to recovery catalog database

RMAN> register database ;

database registered in recovery catalog

starting full resync of recovery catalog

full resync complete

RMAN>