The Better BibTeX Configuration can be found under the regular Zotero preferences pane, tab ‘Better BibTeX’.
The configuration of Better BibTeX is a little baroque compared to the standard Zotero Bib(La)TeX exporters (which only have hidden preferences). The defaults should just work, but here’s an attempt to describe what they do.
Making any change here will drop your entire export cache. This is usually not a problem unless you have a really large library, but you can read about what is involved here.