The sidebar area is used to display widgets. To create a new sidebar and assign it to a page do as follows:

Step 1: Go to Aardvark > Custom Sidebars, click the Add Sidebar link and give your new sidebar a name.

Step 2: Now go to the desired page and scroll down to the settings panel and select one of your sidebars from the Sidebar drop down menu.

Step 3: To change the sidebar on all posts, pages, categories etc. this can be done from Aardvark > Theme Options page.

Step 4: Now go to Appearance > Widgets and drag and drop widgets from the Available Widgets panel over to the widget areas on the right.