How to create and populate app.json file for heroku upload

I'm having some trouble getting my Heroku project viewable and live. After visiting the project domain URL, I'm returned with the following page error: Application error An error occurred in the application and your page could not be served. If you are the application owner, check your logs for details.

I've created the Procfile in the root folder of the project and inside the Procfile I wrote: web: node app.js

I then went to my terminal and uploaded the project to heroku with the following commands:

heroku heroku create ph1933-shopping-cart-demo git push heroku master heroku open

I now have this uploaded to heroku, however it does not have an app.json file in the root directory. How can I add the app.json file into the root folder of the project while having it populate with the appropriate info in order for heroku to accept it and allow the application to go live from the domain URL link. https://ph1933-shopping-cart-demo.herokuapp.com/

I'm using NodeJS and Express.

via Paul Hanna