Install required gems by bundle install
Copy migrations configuration file cp db/config.yml.sample db/config.yml
Create database by hand or using migrations (it requires full privileges to create databases)
Run migrations rake db:migrate DATABASE_ENV=development
Copy application configuration file cp config/environments/development.rb.sample config/environments/development.rb
Run application puma -p 3000
See config/routes.rb file to see all available API endpoints
You can use curl to make request to those endpoints. Just add -H "Authorization: Base64(username:password)" with your own credentials.