I have my blog posts link to Catergories.  When I click on the Catergory menu in my side bar, it can take me to all the blog posts I have assigned to that catergory.  So it takes me to a seperate page.  This has the Main Sidebar set and I have made it empty, but where do I find the link to change what Sidebar is shown there?  Please click on 'Weddings' in Catergories, so you can see an example.  At the moment, the sidebar is empty.

Don't worry I found it.