Help needed for my Forum's Banner

[Windy]

The Forum's URL: http://stirlaughrepeat.s2.bizhat.com

Issue:
I can't get the Banner to fill the width of the Forum Header space. I have tried doing that with a wider banner but all it does is it pushes the Forum's Title and the phpBB's buttons to the right.

Need:
To learn how it is possible to fill the full width Banner at the top of the Forum and the phpBB's buttons to be displayed below the Banner.

Appreciate guidance offered to me.

Thank you,

Windy