aftsq on "Trying to get in - getting blank screen"

Hi folks,
Total newbie who appears to have made a fatal arror.

I tried to add theh following to the functions php so I could do submenus:

"How can I enable the use of Hidden Custom Fields?

I am currently working on settings page where you can enable this feature. In the meanwhile you can enable this by adding this piece of code to your theme's functions.php:

<?php
add_filter('cpac_use_hidden_custom_fields', '__return_true'); // enables the use hidden custom fields
?>"

Well, now I can't get into the site at all - just gives me blank pages.

HELP!!!!!!

http://wordpress.org/extend/plugins/codepress-admin-columns/