I think you switched the meaning of template and textures. Klick on the Textures tab, which is at the right side by default. klick on default.wad. Then you rightclick somewhere in that black area and select 'texture manager' There you can click 'add wad' or 'new wad'. At 'add wad' you can select standard.wad, there are some sample textures from gamestudio, but of course you can add your own as well