How to format SQLPLUS output?

 Hi!

How do I format the below output to be more readers friendly?

select sid, username, event, blocking_session,
   seconds_in_wait, wait_time
from gv$session where state in ('WAITING')
and wait_class != 'Idle';

    SID USERNAME                       EVENT
                        BLOCKING_SESSION
------- ------------------------------ -----------------------
----------------------- ----------------
SECONDS_IN_WAIT WAIT_TIME
--------------- ---------
    183 SERVER                         PX Deq: Signal ACK
              0         0

As you can see its really hard to read.

Thanks for your time!