How to configure rDns in server

Hi!, i’ve a problem in the moment of configure " INITIAL CONFIGURATIONS", i´ve a server with operating system ubuntu server and one public ip, i dont know how to configure rDns.

¿these configure from console?
¿these configure from domain panel?

Thaks.

I’ve explained how to set rDNS here: https://www.youtube.com/watch?v=LkjN5DCWb0o

I’re verified the video, thank you very much