how to run procedure and function

create or replace function myfun return varchar2 is
begin
return 'helo bhai';
end;
/

select myfun from dual;
describe dual;

execute myfun;
select myfun('hello world') from dual;


CREATE OR REPLACE FUNCTION MYFUN2(VAR VARCHAR2) RETURN VARCHAR2 AS
BEGIN
RETURN VAR;
END;
/

SELECT * FROM DUAL;