// You can use the 'Instantiate()' function to clone a GameObject
clone = Instantiate(original);

// You can also set the position, rotation and parent
clone = Instantiate(original, new Vector3(0, 0, 0), Quaternion.identity, cloneParent.transform);

using UnityEngine;

public class example : MonoBehaviour
{
	public GameObject prefab;
    
	// Start is called before the first frame update
	void Start()
	{
		Instantiate(prefab, new Vector3(0, 0, 0), Quaternion.identity);
	}
}

Instantiate(cube, Vector3 (x, y, 0), Quaternion.identity);

GameObject prefab = reference_to_your_prefab_asset;
Vector3 position = Vector3.zero;
Quaternion rotation = Quaternion.identity;
Transform parent = parent_of_instantiated_prefab;

Instantiate(prefab, position, rotation, parent);

using UnityEngine;
using System.Collections;

public class Instantiate_example : MonoBehaviour 
{ 
  public Transform prefab;
  void Start() 
  { 
     Instantiate(prefab, new Vector3(2.0F, 0, 0), Quaternion.identity);
  } 
}

Instantiate(tree, new Vector3(0, 0, 0), Quaternion.identity);