To change controller & view, you need to create your own controller, route & view according to laravel documentation.
To over ride controller -
->Your controller should contain the core path which you want to over ride & your method.
->Route will be provide in default route file & same as controller.
To over ride view
->In laravel's default view , there is folder called 'vendor' , your all view file will be here followed by same directory structure as in bagisto's view. (like Shop & admin)