How to send push notification from web app to Android device using Parse?

We actually do this by sending a push message from mobile to mobile. We are now trying to send a push notification from a web app to mobile devices using javascript. we tried like this

function authentication() {

Parse.$ = jQuery;

  // Initialize Parse with your Parse application javascript keys
  Parse.initialize("app key",
                   "script key");



 var pushQuery = new Parse.Query(Parse.Installation);
    pushQuery.equalTo("channels","Demo");


  var promise = new Parse.Promise();
debugger;


    Parse.Push.send({
         where: pushQuery,

          data: {
          alert : "Hello word" 

    }}, { success: function() {
          // Push was successful 
          alert : "Push was successful"

        },
          error: function(error) {
         promise.reject(error);

        }}).then (function(error) {
          //Marks this promise as fulfilled, 
          //firing any callbacks waiting on it.


        });

   return promise;
}

      

        
        
        
      

    

we get an error like this

Failed to load resource: the server responded with a status of 400 (Bad Request)
code: 115
message: "Client-initiated push isn't enabled.

      

        
        
        
      

    

We've also included Client Push

We are new to Push notification.plz. thanks in advance