Okay! Here it comes.
I'm using JustSkins template Twilight which I have modified. That template have only one sidebar. And I wanted two sidebars. I put in following code in index, page, single.php
<?php include (TEMPLATEPATH . '/sidebar2.php'); ?>
Then I took existing sidebar and named it sidebar2 and made a duplicate of the CSS sidebars naming them sidebar2, because it should have a different look.
Everything is working fine, showing up properly on the site exept for one thing. I want it to show up in admin under Design/widgets. But it doesn't. I can only choose that one sidebar.
In sidebar2.php I changed to number 2 between (). I don't know if that does anything, since I'm not good at programming.
<?php if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar(2) ) : ?>
I think I might forgot to put some output telling it to show up in admin interface. But I don't know where.
I'll be very greatful if you guys help me out.