I'm not sure whether I understood your problem. But if you are asking how to set google as your search engine in firefox you can do that as I'm saying.
In the 'search box' at the right top of the brower, which shows your current search engine, there's a 'very small arrow head pointed to down' at the beginning before mentioning the search engine's name. Click that arrow head and select Google instead of Bingo from the dropping down menu. And your search engine will change to google then.