angular to fetch the json service from http

I have seen your shared codepen. So Ricky as you are new to angularJS, I would suggest you to read the documentation related to angular 1 from here: Angular JS - Documentation

Now coming to your requirement, you required to call an external API and use the data from the result. For that you have to learn about the $http in angularJS : $http documentation

Coming to the code, angular supports the dependency injection. The code you have shared is a mystery for me like what fetch(postsUrl) function is doing? Where is the declaration?

Cut and short, the implementation should be clear and readable. Here is my refactored one:

var app = angular.module("blogApp", []); //here you defined the ng-app module

//you are initializing a controller, you need to inject $http for calling the API 
app.controller("mainCtrl", function($scope, $http) {

        //Declaration of the posts object
        $scope.posts = [];

        //Onetime initialization of the API Endpoint URL
        let postsUrl ="https://jsonplaceholder.typicode.com/posts";

        //A method for getting the posts
        function getPosts(){

           //We are calling API endpoint via GET request and waiting for the result which is a promise 
           //todo: Read about the Promises
           //A promise return 2 things either a success or a failure callback, you need to handle both. 
           //The first one is success and the second one is a failure callback
           //So in general the structure is as $http.get(...).then(successCallback, failureCallback)  
            $http.get(postsUrl).then(function(response){

               //In promises you get data in the property data, for a test you can log response like console.log(response)
               var data = response.data;

               $scope.posts = data; //Storing the data in the posts variable

                //Note: you don't need to call the $scope.$apply() because your request is with in the angular digest process. 
                //All the request which are outside the angular scope required a $apply()
            }, function(err){
               //log the err response here or show the notification you want to do
            });
        }

        //The final step is to call that function and it is simple
        getPosts();         

});

Coming to the second part to show the data. You have to use the ng-repeat documentation, it is as ng-repeat="var item in collection track by $index". It's documentation is here ng-repeat

So you html should be in this structure:

<div  ng-repeat="var post in posts track by $index"> 
    {{post.userid}}
    {{post.id}}
    {{post.title}}
    {{post.body}}
</div> 

Now it is onto you to learn and implement.