Make "Buy It Now" and

I contacted the theme support and asked about changing the “Buy It Now” and the “Reserve Price” into a option and not a requirement and they said “you need to modify the details for the add listing page to change that. please edit the file: framework/class/default_auctions.php.” I cant find this file and I have no idea what to look for and change when I do. I really need these to be an options.