Here's a quick guide on how to create new Add-ons for your menu:
- Select Add-ons and on the upper right of your screen press New Add ons
- Put the name, max items and necessity (whether the add-on is optional or required) and press Save Add on
- Once saved, press Add items to create choices for the add on
Note: To attach add-ons to a menu item, you can refer to this article