Myrddin is correct, these templates are simply texture files that you open in Paint.net. When you download them, they come zipped, so you need to find the zipped file and then extract the textures themselves with Windows (if you use Windows) or another application such as Winzip or Peazip.
Once that is done, you go to File > Open in Paint.net and choose the unzipped file. The full 6 layer file should be the first one in the list.
Hope this helped.