How to I add objects,shapes, and characters to the field?

I was trying to add a new object to my game but I didn't know how to add, an object or character and I also downloaded the standard assets and found the character scripts but I don't know how to add an actual character.

 

It sounds like you need to follow some of the basic tutorials from the Unity homepage. You add an object to the scene by dragging an appropriate object from your project directory into the scene view or hierarchy, for example a model, prefab or sprite. The Standard Assets should have a prefab for a CharacterController gameobject.