Each individual user can configure his/her knowledge search providers. This blog post demonstrates how to configure knowledge search providers.
1. Go to knowledge search and click link Manage Knowledge Search Provider under search term textbox.
2. Click Add
3. Follow instructions about how to create a search provider and fill two textboxes – the name and the URL, Click OK
4. Repeat step 2 and 3 to create up to 10 search providers. For example, TechNet, MSDN. If you have a SharePoint site within your organization, you can search document libraries on the SharePoint site.
5. Click Close and go back to knowledge search window, type "Knowledge" in search term textbox and click Go
Each registered search provider will be displayed in a separate tab. Click on each tab and you should see the following: