controlDefinition [window

Jun 11, 2014 9:25:57 PM de.lessvoid.nifty.loaderv2.types.ControlType internalApplyControl
WARNING: controlDefinition [window] missing

^^ That is what it tells me when I try to load a control window missing. I intend to use the one in this link:

However only the text in my xml file shows up. Here is the code:

    <layer id="windows" childLayout="absolute">
        <control id="window" name="window" title="Please Drag Me Too!" width="500px" height="400px" x="400px">
            <text text="I'm Another Window!" font="Interface/Fonts/DifficultyMenu/STechMono14px.fnt" color="#eeef" valign="center" width="100%" />

I have assumed that all I have to do is use this “control” of yours to be able to use a window, however, is it the case that I have to “create” my own window before using it? I’m kind of confused on the control idea as a whole.