how do I add code instead of a link to a slider button?

Hi There, I want to add a leadpages optin where the button is on the slider on the home page and the theme only has a place to add a url link. How do I add the code for the opt-in box that I want to have show when someone clicks the link on the slider on the home page? Please let me know. Thanks, Sandra

The website is frontpageagency.com