Instantiate onMouseDown

You can use Raycast to get a point. Object to get the point to set position of your Object instance need to have a Collider, and rigidbody to better physic operations, set it kinematic if you dont need for some else thing.

 public Camera yourCam; // Reference of your Camera
     public Ray ray;
     public RaycastHit hit;
     public LayerMask yourLayer; // On Inspector, you can set wich layers detects the ray if you not set nothing, ray not detect nothing 
 
     private void Update()
     {
         ray = yourCam.ScreenPointToRay(Input.mousePosition);
 
         if (Physics.Raycast(ray, out hit, yourLayer))
         {
             Debug.DrawLine(yourCam.transform.position, hit.point, Color.green); // If your ray detect any collider, a green line to the impact point is showed
 
         } else
         {
             Debug.DrawLine(yourCam.transform.position, ray.GetPoint(10), Color.red); // If your ray dont detect nothing, a red line in direction to the ray is showing
         }
     }