Users have normally no problem with multitexture terrain, as this is pretty straightforward. Look into the description in the manual:
http://manual.3dgamestudio.net/amaterial2.htmBut you should place your terrain in WED. The current version of the multitexture shader supports terrain lighting, so generate a lightmap for terrain. AFAIK it also works without lightmaps, but then does not look as good of course.
If you can't get it to work, just contact Gamestudio support. When you own Pro, you're entitled - in fact you've already paid for it
. They can also look into your files when necessary.
