How do i hide the payment plan option on my order form?

Using the Product / QTY criteria isn’t working to set up a product that doesn’t have the payment plan option - my current product is less than the finance charge so it doesn’t make sense to allow a payment plan - so I either want to allow a payment plan for a specific product that wont’ show on all my other products (at the moment using the Product QTY criteria in the order form is just adding this payment plan to all my other products. I just want to hide the code and saw somewhere it said put this in the CSS part of the theme but I don’t know where to put it in the order form…

display: none;