In a browser go to your Heroku Dashboard

• Login if required.

Select your app.

Select the Resources tab.

• If you see Heroku Postgres :: Database go to step Select the Deploy tab.

• Else: Type postgres in the Add-ons field and select Heroku Postgres

Select the Deploy tab.

Scroll to the bottom of the page, you'll need the name of your heroku app repo.
This might be different than the name of your github repo.

Connect local repo to existing Heroku app. DO NOT TYPE $

$ heroku git:remote -a foobar

Push to Heroku

$ git push heroku master

Connect to your Heroku App database

$ heroku pg:psql

• You'll see something similar to:

Create tables, populate data, etc.
Example:

-- create a table
CREATE TABLE foobar (id SERIAL, foo VARCHAR(24), bar TEXT);

-- add data
INSERT INTO foobar (foo, bar) VALUES
('tomato', 'is it a fruit or vegetable?'),
('pear', 'so many pears to chose from.'),
('apple', 'honeycrisp apples are my favorite.');

Open a rails model file from the app/models directory

$ app/models/foobar.rb

Edit the database connection
You'll need to do this for every model.

class Foobar
  attr_reader :id, :foo, :bar

  # if heroku, use heroku psql db
  # --------------------------------------------------
  # if statement shouldn't require change
  if (ENV['DATABASE_URL'])
    uri = URI.parse(ENV['DATABASE_URL'])
    DB = PG.connect(uri.hostname, uri.port, nil, nil, uri.path[1..-1], uri.user, uri.password)
  # --------------------------------------------------

  # else, use local psql db
  else
    DB = PG.connect(
      host: "localhost",
      port: 5432,
      dbname: 'foobar')
  end

  def initialize(opts = {})
    @id = opts["id"].to_i
    @foo = opts["foo"]
    @bar = opts["bar"]
  end

  # CODE HERE
  # ...
  # ...

end

git push to github and heroku.

You can now user your local database while developing, and heroku will use its database on production.