Create an account on Heroku. This is a free process, however they may ask you for a credit card in order to ensure that you won't try to create spam accounts.
Install the Heroku CLI. The following link will walk you through how to install the CLI (command line interface) on your operating system: https://devcenter.heroku.com/articles/heroku-cli - this will give you the ability to use Heroku command on your system.
Create a git account. You can perform this task at Github.com or Bitbucket.com. I personally prefer Github and that is what i use on my personal and professional development projects.
Install git on your system. This link will help you walk through how to install git on your operating system of choice: https://git-scm.com/book/en/v2/Getting-Started-Installing-Git
With git and the Heroku CLI installed on your system, you will need to 'wrap' your project as a git repository. So change into the root of your React project and type:
Create a remote repository on Github (or Bitbucket) and create a connection to the remote repository between your local repo and the remote repo.
Create a Heroku application with the terminal command:
Push up your code to the application with the command:
This assumes that you're using the starter code from the JS Builder starter applications here: https://github.com/bottega-code-school/js-builder