Woocommerce forms

I have used the woocommerce add-on to create a form to add to my product but am confused as to how to do the calculations.

I have a form with three dropdown options - Birch, Oak, and Walnut. I use separate values and make the dropdown saved values 0, 5, and 10 meaning Birch option adds 0 to price, oak adds 5 and walnut adds 10. I have a “total” field set as a calculated field, but I am confused as to how to tell my form to add the appropriate value to my product price. The knowledge base is too vague for me to understand how I am supposed to do this. It simply says I need a calculation field to "link up" with the price. I can see my form on the product page, but the total does not change when I select different options. How do I add the saved values of my dropdown field to the woo product price?