How do I print output in new line in PL/SQL?

You can concatenate the CR and LF:

chr(13)||chr(10)

(on windows)

or just:

chr(10)

(otherwise)

dbms_output.put_line('Hi,'||chr(13)||chr(10) ||'good' || chr(13)||chr(10)|| 'morning' ||chr(13)||chr(10) || 'friends');