Just go to https://dashboard.heroku.com/apps/YOUR_APP_NAME/deploy/heroku-git.
Install the Heroku Toolbelt
Download and install the Heroku Toolbelt
If you haven’t already, log in to your Heroku account and follow the prompts to create a new SSH public key.
$ heroku login
Clone the repository
Use Git to clone YOUR_APP_NAME’s source code to your local machine.
$ heroku git:clone -a YOUR_APP_NAME
$ cd YOUR_APP_NAME
Deploy your changes
Make some changes to the code you just cloned and deploy them to Heroku using Git.
$ git add .
$ git commit -am "make it better"
$ git push heroku master