You need to go back into your dash board for the next few steps.

1. Click on Appearances. Custom Sidebars should now be listed. Click

   

2. All the sidebars you have on your site will be listed in the box on the left. Here you will need to select the boxes you would like to substitute for a custom sidebar. This means that any ticked boxes will be able to have alternate information in them depending on the page/post/category you chose to show them.I have inserted a screen shot (a feat in itself) so you know what to look for.
3. If you want to substitute more than one area, hold ctrl and click the extra boxes.
4. Click Save Changes.