Given the inexplicable stubborness of your copy of WadAuthor, all I can say is: ditch it, use DoomBuilder instead. While a441's guide will be trickier to follow since it's not really designed for that level editor, it'll still cover most of the basics, which apply for both editors (things like the thok barrier, the sky effect, why it's important to know what needs to be textured (DoomBuilder has this nice feature of letting you know what textures are missing for a linedef, so don't worry about it TOO much; I think WadAuthor does too, though I can't really remember), creating water and FOFs (DoomBuilder does it more or less the same way), and stuff like that). I believe I linked to the config on the Suggestions and Help forum very recently, so go look for that.