How do I change from AVG Secure Seach to Goggle as the default search enging bor the the search bar and when I open a new page?

When I load Firefox, the default search engine goes to AVG Search. I'd like to change it so that the default search engine on the search bar is Google. In addition, when I one a new page, the new page home page defaults to AVG Search. I'd like opening a new page to default to Google. My initial home page goes to the Wall Street Journal, which I want to keep, but want to change for the search bar and when a new page is opened to Google.