AngularJS Services (Update/Save)

New to AngularJS and trying to get a grasp of the framework, and trying to build a basic CRUD app. I can't seem to figure out what is needed to Update an existing record. Here is my service:

 angular.module('appServices', ['ngResource']).
factory('App', function ($resource) {
    var Item = $resource('App/:AppId', {
        //Default parameters
        AppId: '@id'
    }, {
        //Actions
        query: {
            method: 'GET',
            isArray: true
        },
        getById: {
            method: 'PUT'
        },
        update: {
            method: 'POST'
        }
    });
    return Item;
});

I can run a basic Get all query, and getById to populate an edit form, but that's where I'm stuck. Here is example code for getById

 $scope.apps = App.query();

$scope.getEdit = function(AppId) {
    App.getById({id:AppId}, function(app) {
        $scope.original = app;
        $scope.app = new App(app);
    });
};

$scope.save = function() {
    //What type of information should go here?
    //Do I need to make changes to the appServices?
};

I guess, I'm just not sure what's next concerning Updating existing information, or how the "app" object gets passed to the API, can anyone point me in the right direction, or show me a quick update method?