Step 1. Go to the Inventory>>Categories page.
Step 2. Click on the category/subcategory you would like to delete.
Step 3. Scroll down until you see the Delete button.
Step 4. Click on the delete button.
A warning message will come up letting you know that by deleting this category you are deleting everything inside of it. So if you are deleting a parent category then all of its subcategories will be deleted as well. If you are okay with deleting JUST the stuff that is beneath THIS category then:
Step 5. Click Ok.