Hi, I made a terrain with GeoScape then I exported it to a MDL5 model so that I coul import it into WED. Now, I want this terrain to be used as an actual terrain however, when I try to build this map it says it has no geometry (because my terrain is an entity and not a terrain). How can I make sure my GeoScape MDL file becomes a terrain?

Just add a small geometry block to your level, it can be really small if you want.

Yeah that's what I did but I was wondering whether or not my real models (not the terrain but actors) are then placed upon the block or upon my entity since it's theoretically an actor as well

The block needs to be no smaller than 2x2x2 quants. I use 4x4x4 myself which is so small, you'd have to be pretty much right on it just to see it. I hide this block inside an existing model and have it as a sky block to get skies to be able to be rendered.

The block is just there so when you build the level it shows that there is geometry in your level so it can build. WED levels don't compile without at least one geometry block. Now you can place your Actor models on top of your entity terrain and they will act upon the terrain and not upon the block (block doesn't even have to be seen, you can hide it).

The terrain isn't actually theoretically an actor as well unless you put the action of it on it. Terrains general don't have actions unless it's for shaders of some sort or the other. In your levels case it should just react like it's a block and that you can walk on it. I mean you can try all this out for yourself real easily in WED.

I've otherwise stated that you can hide this block. In my case, I hide it in an existing model (and make it have a sky texture to get sky objects to work). Of course, you don't have to have it as a 64x64x64 size or something big like that, 2x2x2 is sufficient enough, but I suggest using 3x3x3 or 4x4x4 to prevent possible build errors.

Okay, thanks for the brightening.
Sorry if this post may seem stupid but I'm new to 3DGS and totally new to authoring systems.

Typical beginner's questions. These things get answered quickly, often in the matter of a few minutes. The expert-level questions could take much longer to get answers on.

I'm pretty much a master at 2D and have little experience with 3D things. I can write scripts for things considerably well, but I do have limits. You'll get there. My statement in my signature is a very powerful guide to go by. Don't start off doing very advanced projects, do something at your level. By doing so, you gain experience the fastest and the easiest.