1. Click Modifiers Categories and click ‘plus’ + button 

2. After that, key in the details. Then, click Submit button

3. It would be like this

4. Go back to Item Modifiers, click +Add Item

5. Click +Add Item (For ADD-ON Category) and put the detail then, it will like this.

6. Update Settings at your iPad and when click the item, result will be like this