Relevanssi AJAX search, where to put the code

Hello Enfold,
I use relevanssi for my search, and it works great. I found this http://kriesi.at/documentation/enfold/use-relevanssi-in-search-instead-of-the-default-search/ to make the ajax results also relevanssi. But it doesn’t say where to add the code. I already had some major errors do to bad editing of the functions.php So I would like to know for sure where to add the code. At the top, at the bottom, between something, within some tags. I have no experience with php. So if someone could be as specific as possible where to paste the code, that would be awesome!

thanks