To import a dll or use any object not in the project's namespace you must add it as a reference. Right click on "References" and "Add Reference"... Click on the Browse tab and find your dll.
Now that it is added as a reference you can use the class even though its not in your main namespace. You still might have to added the using statement in the the scope of your class.
Now this is using Visual Studio Standard Edition, but I assume the express edition allows you to add references...