Looking to Finish activating Shop Pay Installments

I am attempting to add Shop Pay Installments to my store.

The instruction say  "You need to add a snippet of code, {{ form | payment_terms }}, to each instance where you have a product form in your theme.'

For most themes, product forms can be found within the product-form.liquid file or featured-product-form.liquid. For some themes, you might need to update the product-template.liquid file.

I can't seems to locate product-form.liquid or how to update product-template.liquid.

Any suggestions?