newbie 5.1 begin with world creation

Hi, I followed 2 tutorials on PaperZD (Cobra Code on YT, it’s great).

Now I’d like to start creating the environment!

I want the first level to be a sci-fi submarine military base. It’s probably not easy but I think with this asset pack: Polar Science Facility | Sunset Version | Free Environment Kit - YouTube it’s doable.
Problem is, there’s not even a demo level so I really don’t know where to start, do you know a tuto that could help me? Any advice? Thanks in advance :smiley: