Login to your account at https://squareup.com/us/en and go to your dashboard. On the dashboard, go to Items → Modifiers. Click on Create a Modifier Set. There, you can fill in a name for your modifier set, create new modifiers, add price for modifiers, etc. When you are done, click Save to add your new modifier set. Next, click Apply to Items to select items that you want your new modifier set to apply to, and click Save. Go to https://squareadmin.grubbrr.com/ and click on the Sync Data from Square icon (at the top right corner) to sync your changes. Finally, click on the Tablet Icon on the top right corner to sync data to the kiosk.