Here's how to create a new modifier group:
Go to the Dashboard > Restaurant > Menu > Modifiers
Click on Create Modifier at the top
Enter the following information:
Display Name: the name your guests will see on the menu
Description: a description of the modifier (does not show up on the menu)
Amount: the cost of the modifier (if free, put $0.00)
Selection: the minimum and maximum quantity of this modifier that a customer must select when ordering
Options and Allergens: choose if any of these apply to your modifier
Variation Groups
Apply sales tax for this item: toggle on or off
Click Save Modifier at the top when done