If you are asking something like this then your knowledge is most likely at the level where you would benefit from reading up on basic 3D theory.
Going from 2D to 3D is not just "a little" harder, it is a completely different ballgame. Not only that, but GameMaker makes it especially difficult, as far as game engines go. I want you to read through that entire article. For every term you come across in that article that makes you ask "what is that" or "how is that implemented" I want you to search the internet and learn about it.
Once done, try implementing this yourself. When you get stuck come back here, show us what you have tried, what is going wrong, and what your desired outcome is. We can then guide you.
I say this because setting up even the most basic scene requires:
Knowledge of vectors and how they work
Knowledge of how rendering works via matrices (you must build model, view, and projection matrices)
Knowledge of how to build 3D primitives (vertex buffers, yay)
Knowledge of how to transform 3D primitives (you must build transformation matrices and apply them to your model matrix)