injecting angular-flexslider with mean stack (angularjs) app.js error

so im trying to use flexslider im injecting it to my mean stack (angularjs) application (angular-fullstack-generator) on the app.js file after installing it with bower but its not finding the module at all.
i added the file index.js on the bower_components to export the module name but still getting the same error anyone managed to make it work ? thanks.