To start off I suggest you have a graphics program which will allow you to browse through the graphics in your env folder, I suggest Paint Shop Pro. If you followed the instructions for SinED correctly, you should have your env folder in the directory *:\tools\sin\base\ Browse to this directory with your graphics program and choose your sky texture set, for example "intro_*.tga". All of the intro_*.tga files pertain to this env map. There is a intro_bk.tga, intro_dn.tga, intro_ft.tga, intro_lf.tga, intro_rt.tga, intro_up.tga. All of these files make up the sky for the Intro theme. Now lets say I made the decision to use the Intro set I will have to take note of the name "intro_", I will explain this in the next paragraph.

Now to see how to make a sky, start up SinED, create a small room with a Player-Start and lights. Next press "N" to bring up the entity editor. Click once on the worldspawn (don't double click on it). Click in the Key field and type in Sky and below in the Value field enter intro_. This intro_ tag is the value of the sky theme we chose in the previous paragraph. Hit Enter to register the change. Now this level will have the specified sky set throughout, in places that you specify.

Next up is to tell SinED where you want the skies to be. Now in the room you built, select the ceiling and press "S" to bring up the surface inspector. In the Surf Inspector, checkmark the checkbox beside the word "Sky". Save and compile, then load up the level and look up, you now have a sky.