New Post: Help Getting Started

Hello,
I'm sorry for such a silly question, but I am not able to get started using this. I followed the directions and:
1) Created a reference to the Xceed.Wpf.Toolkit.dll file
2) Edited the properties of the DLL to unblock it
3) Added this statement to the code-behind "using Xceed.Wpf.Toolkit;"
4) Added this namespace to the XAML xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit"

In the XAML editor I can type <xctk: and the option for DecimalUpDown appears and even the parameters appear. When I close the tag, there is a blue line under it with the message that "The name "DecimalUpDown" does not exist in the namespace "http://schemas.xceed.com/wpf/xaml/toolkit"."

I thought that I followed the directions but obviously I made a mistake someplace along the way.

For what it is worth, I tried to add the controls to the toolbox following the directions from June 2, 2013 on this page:
Comments on documentation page
Although the Toolbox tab shows the new controls, when I try to insert them an error box displays saying that the following reference has been added to the project:
Xceed.Wpf.Toolkit, Version=2.9.0.0, Culture-neutral, PublicKeyToken=somenumbers" and that I should press OK to restart the XAML designer.

The OK button doesn't seem to do anything and the error always appears. I don't see where anything was really added. The Toolbox tab would have been a nice solution...

Also, I am using VS Community 2015 and the .NET Framework version is 4.6.01055.

Thank you for the help.