If you have already set up ItemAttributes, then the list of Item Attribute Types will show here. You can toggle them on/off to select whether this ItemObject can make use of the ItemAttributes of each type.
Below, you can select which specific Item Attribute objects this Item Object can make use of.
This does not add the Item Attributes to the object, rather it flags whether or not the GameItem Object can receive the specific Item Attributes during the game.