This contains several steps.
1: download a model of the item you want to use. For this post, I'm going to assume I'm using MC!'s Sobi Mask model.
2: Import the model into your map.
3: Open you Object Editor, and go to the Abilities Section.
For this example, I'd go to the ability associated with the Sobi Mask.
4: Change the Art-Target section( this should be blank) to your imported model.
5: change it to wherever it would attach, e.g. 'head'\'hand'-'left'\etc.
Hope this helps you.