Open up the sidebar.php file and take a look for a line looking like this:
<?php if ( !function_exists('dynamic_sidebar')
|| !dynamic_sidebar() ) : ?>
If that's in there or something simular, then the theme can support widgets. No offense intended towards the creator of the theme but seems like half the themes over at themes.wordpress.net tagged as "widget ready" aren't. *grumble*
The other issue may be you didn't install the plugin correctly or have activated it yet. You may want to check your installation walkthru and your plugins page.
hope this helps,