In this example, we will create an add-on, “Custom text printing” to our t-shirt product.

Step 1
When your are editing a product, scroll down to Product Data, and click Add-ons on the left.

Click on New Addon Group button.

Step 2
Select Addon type. It could be checkbox, textbox, dropdown select and etc.

In this eg, we will use textarea for our “Custom text printing” add-on.

Step 3
Enter the name of our add-on.

Enter and add New Option.
In this example, we add “Front” and “Back” for custom text printing for our T-shirt product.

Repeat Step 1 to Step 3 to add other desire add-on.

In front-end, when customer selecting the add-ons. The add-on price get updated.