I put it in there but it's not working.
your question was where does this code go... not would it work in your site.
this put it in the index.html head.
the code says add this (css codes) when this (html = page) is rendored;
- if you put it in your site propreties it will load on every page of your site,
- if you load it into the home page propreties it will only load on the home | index page and
- if you put it in an iframe or div then it will only load in that element