Hello.
Here you go:
var array = new Godot.Collections.Array<Node>();
array.Add(new Node());
var list = new System.Collections.Generic.List<int>();
list.Add(1);
list.Add(2);
list.ForEach(i => GD.Print(i));
The Godot Array is best for Godot Types (Nodes, Textures, etc.) and the .NET List is good for everything else (float, int, string, etc.).