1. With Mission Editor, Click World Editor Inspector, Sky, Change the skybox.
2. With world editor CREATOR, (I'm sorry my mission editor doesn't work) Look through all the options until you find sharp trees, pick the tree you want.
3. In world editor inspector, click sun, change the lighting and ambient. Add fog with world editor creator and change it the same color. Then click File/Edit (I dint remember) and relight mission
4. Save map as (Yourmapname.mis) into the addons folder. Then go into the addons folder, and get yourmapname.mis and Yourmapname.ter and put them in a folder (Map_Yourmapname) Add a yourmapname.txt(Notepad file) with a
Name: Yourmapname
Author: k772
Description: Small description
Add a yourmapname.png, which is a picture of your map
Zip the folder.
5. Make your own.
6. Paint Textures Option, click change and pick your desired texture
I hope that helps a lot