Start from scratch, create a brand new OctoberCMS:
composer create-project october/october myoctober
Change the config the external environment:
php artisan october:env
Overwrite the config/app.php and config/cms.php from this repo, and copy Procfile into project root.
If you are not under version control already, create a local repo:
git init
Important: remove composer.lock from .gitignore!
Log in to heroku and set up the cloud database:
heroku create
heroku addons:create heroku-postgresql:hobby-dev
Push the codebase:
git add . --all
git commit -m "Heroku setup"
git push heroku master
Log in to the app with an on-off dyno, and run the db migrations
heroku run bash
> php artisan october:up
Open heroku app and login with admin/admin under /backend url. It should work :)