Create Procedure

Procedure:
create or replace procedure hello is
begin
DBMS_OUTPUT.PUT_LINE('hello');
end hello;
Call:
SET SERVEROUTPUT ON;
begin
hello;
end;
/

Connect to SQL*PLUS

C\:>sqlplus
input username, password
or run
SQL commandline from Oracle menu.
Simple SQL:
SQL>select * from table;
Simple PL/SQL:
SQL>SET SERVEROUTPUT ON;
2 BEGIN
3 DBMS_OUTPUT.PUT_LINE('hello');
4 END;
5 /