How to add an Inventory Modifier to an item?

First, you need to create Modifier Groups to visually classify your modifiers into neat sections. To add a new Modifier Group:

Step 1: Visit Setup > Global Settings > Modifier Groups.

Step 2: Click the Add Modifier Group button.

Step 3: Enter the details and click Save. 

To add an Inventory Modifier for a menu item:

Step 1: Visit Setup > Menu Setup.

Step 2: Search for the menu item you want to add a modifier to in the search field.

Step 3: Click the Edit button against the menu item.
Step 4: Scroll to the Item Modifiers section.
Step 5: Under Inventory Modifiers, select the Modifier Group from the dropdown.

Step 6: Then, type and select the Modifier Name from the adjacent search field.
Step 7: Enter the price for the modifier.
Step 8: Click Update.
Step 9: Finally, click Refresh POS Menu Items.