(Theme Interface Pro) Add HTML To Footer Column Permanently

Hello,

I have begun making a website for my business and have become stuck with adding some html code to a footer.

I have xtml html code plugin for my other footer widgets which works for other html code but the HTML code for the widget I am currently attempting to install will not work with the plugin because the plugin alters the code to short code.

I have spoken with the developer of the original html code and they have stated that it must be used exactly as it is.

So that leaves me to alter html for the very first time.

Can someone explain where I can find the relevant part of the theme to add code?

Daniel