Make required field store info with buy now button also, not just add to cart

[jorgeisaacart]

Hi I'm using an app called Advance Product Options which lets me put a text box as a required field on the product page before anyone makes an order. It used to work for the 'buy button' but now it doesn't. Now it only works for the 'add to cart button' on the product page. whenever I click the 'buy button' without even typing anything on the required text box field it bypasses it. What code can make it work again with the 'buy button and store the info place on the text box in the checkout like it does with the 'add to cart' button? Now whenever I turn the feature on the app to work on the buy button it just turns gray, because of the new shopify updates. What can I do?

[jorgeisaacart]

I'm trying but I can't find the area you mention for the first option and in the second option I can't find the cart.liquid,  is there a way you could do it?

[jorgeisaacart]

Could you help me in writing the code in the correct place? I can't get it to work