The Sidebars module lets you create multiple sidebars you can add to your theme.
The module cha be activated or deactivated from the correlated Modules section.
If the module has been activated, you can create your sidebars in YIT Plugins -> YIT Sidebars.
Add the name of the new sidebar anc click on the Add button.
Now your sidebar is ready and it can be customized with all widgets the theme offers.