You learned how to widgetize the sidebar during the tutorial series, but I never showed you how to turn on the widget plugin. Here it is:
Installation
- Download the Widget plugin from Automattic.com.
 - Upload it to your wp-content/plugins/ folder.
 - Go to the Plugins page of the administration panel.
 - Activate the Sidebar Widgets plugin.
 
Customization
- Go to the Presentation page of the administration panel. If your theme is widget-ready, you will see the Sidebar Widgets link next to the Theme Editor link.
 - Go to Sidebar Widgets.
 - From there, drag the little boxes into the big box.
 - Rearrange the little boxes to the order that you would like each to appear.
 - Click Save Changes.
 - If you leave the big box empty then your theme will use its default sidebar instead of the widgetized version.