this depends on your website code to begin with
if you have a CMS like joomla or WordPress then you would most likely need to code a plugin/module or pay for the development of a plugin/module to interface with the payment gateway (assuming that one does not already exist)
if your site is just static html and php forms etc, then you should be able to integrate any neccesary html into that without issues as long as they follow the relevant guidelines and correctly process the required data
