How to access a child sprite of a sprite sheet from a directory?

I would like to set an icon to an item from code. Here's what I have thus far:

public enum ItemType { Item, Tool, Weapon, Block, }

 public string itemName;
 public int itemID;
 public string itemDesc;
 public int itemDurability;
 public Sprite itemIcon;
 public int itemAttackPower;
 public ItemType itemType;
 
 #region Constructors
 public Item ( string name, int id, ItemType type )
 {
     itemName = name;
     itemID = id;
     itemType = type;
     itemIcon = Resources.Load<Sprite> ( "ItemIcons/" + name );
 }

The name of the icon file resides in the resources folder with a file name of that of its item. It is, however in a sprite sheet (named "Icons") so my question is: How do I access the file from a directory? (as asked in the title.)

I'm a novice programmer so any advice would be greatly appreciated! :)

Thanks!