Created Unassigned: How to use the "Extended WPF Toolkit"-Forms? [22162]

Hi guys,

I'm using the Visual Studio 2013 Community Edition and .NET Framework 4.5.2 and can't solve this prob:
i just downloaded the .dll's of "Extended WPF Toolkit" and installed the "NuGet"-Package.
Then i created a new tab in the toolbox and added the dlls.

After i choosed which controls i want to add i clicked ok and the message appeared:
(quick translated from german)

the following controls are added successfully to the toolkit but are inactive in the current designer:
<list of all "X WPF TK" controls>
Be sure that the controls you added are compatible with the designer and the .NET Framework-Version.

Can anyone tell me where my problem is?
how can i check of my "designer" or the framework are compatible?

Thanks, mac