Open the file functions/sidebars.php and find this piece of (probably repeated) block of code:
register_sidebar(array( 'name' => __( 'Blog Sidebar', 'ci_theme'), 'id' => 'sidebar-blog', 'description' => __( 'Sidebar on blog pages', 'ci_theme'), 'before_widget' => '<aside id="%1$s" class="widget %2$s group">', 'after_widget' => '</aside>', 'before_title' => '<h3 class="double"><span>', 'after_title' => '<span></h3>' ));
This code is taken from the aegean theme but it should be similar to every theme just with different wording.
Copy this code, leave a return line after )); and paste it again.
You should change three things:
'name' => __( 'This is the name of your sidebar', 'ci_theme'), 'id' => 'your-sidebar-id', 'description' => __( 'This is the description', 'ci_theme'),
Those three values should be changed, and write down the ID that you selected for your new sidebar.
Then whenever you wish to display the widgets of your sidebar, this is the code that you have to put in a .php theme file:
<?php dynamic_sidebar('your-sidebar-id'); ?>