First of all, do you know what namespaces are used for in XML and how they are commonly used? Probably not, most people don't really understand them. So I would suggest you read a tutorial about namespaces. I am not impressed by the w3schools tutorial, they are quite superficial. The namespace tutorial at zvon.org is more thorough.
When you have done that, I found this paper on how to use namespaces in schemas that looks like it goes through how to configure things quite well.