How to insert terrain, and other objects?

I’m new to Unity, and I am trying to make a simple 2D game, but I am not sure how to insert terrain, sky or characters, could someone give me a sort of walk-through? I’m sorry if I sound stupid, but have no experience with this. Thank you.

This forum is for specific technical questions. If you want to learn how to use Unity, please follow a tutorial. E.g.:

There are a lot of 2D tutorials for Unity out there. Start from the bottom and learn Unity by following one of them. This one for example is quite good: Unity 2D Tutorial. A quick google search will turn up many more if you need it.

to insert terrain:

  1. Across the top bar, select GameObject.
  2. Go down to 3D object.
  3. Select terrain (4th from the bottom).