Help with a script.

I've got this health bar that follows the player around, but I'd like to make it stick to the bottom left of the screen instead. Can somebody please help me with this? I'm VERY bad at coding.

Here is the script: using UnityEngine; using System.Collections;

 [RequireComponent(typeof(PlayerStatController))]
 public class PlayerInfoBar : MonoBehaviour
 {
     public Vector3 offset = new Vector3(0, 2.5f, 0);        // Offset for the health bar position relative to object position
     public float barWidth = 100;
 
     private Rect _barRect;
 
     private Vector3 _worldPosition = new Vector3();        // Transform position + offset position
     private Vector3 _screenPosition = new Vector3();    // Screen position for drawing health bar
 
     private bool _visible = false;                        // Health bar is visible or not
 
     private PlayerStatController _playerStatController;    // Reference to Player Stat script
     private Transform _t;                                // Reference to object transform
     private Color _barColor = Color.cyan;                // Used by the Infobar
 
     public Color BarColor
     {
         get { return _barColor; }
         set { _barColor = value; }
     }
 
     void Start()
     {
         _t = transform;
         _playerStatController = GetComponent<PlayerStatController>();
     }
 
     void Update()
     {
         // Set health bar position
         _worldPosition = _t.position + offset;
 
         // Check to see if health bar is within the camera's view
         Vector3 viewPoint = Camera.main.WorldToViewportPoint(_worldPosition);
         _visible = (viewPoint.x >= 0 && viewPoint.x <= 1 && viewPoint.y >= 0 && viewPoint.y <= 1 && viewPoint.z >= 0);
 
         if(_visible)
         {
             // Update screen position for drawing the health bar
             _screenPosition = Camera.main.WorldToScreenPoint(_worldPosition);
 
             float x = _screenPosition.x - barWidth / 2f; 
             float y = Screen.height - _screenPosition.y;
             _barRect = new Rect(x, y, barWidth, 20);
         }
     }
 
     void OnGUI()
     {
         // Draw the health bar if we can see it
         if(_visible)
         {
             GUI.color = _barColor;
             GUI.HorizontalScrollbar(_barRect, 0, _playerStatController.health, 0, _playerStatController.maxHealth); // Displays a healthbar
             GUI.color = Color.white;
             GUI.contentColor = Color.white;
             GUI.Label(_barRect, _playerStatController.health + "/" + _playerStatController.maxHealth); // Displays health in text format
         }
     }
 }

Thanks for the help!