This is a browser option. If you use more than one browser, you must do this in each browser. Frequently the search engine is changed when you download free software without unchecking the option to change your search engine.
If you are not seeing the Menu Bar (File, Edit, View, etc.) at the top of your browser, right click in an empty area at the top of the screen and click on Menu Bar. In Firefox go to Tools, Options, Search. It is best to uninstall the search engines that you do not use.