ORM Standalone - need a simple example

hi, i am familiar with cake. Now I want to use the ORM standalone package in an existing legacy php project. Installed with composer and read all the hints in the readme.md.
Nevertheless I do not where to put the code and how to run ist.
Even starting just the bootstrap.php raises an error (seel below).

Does anyone have a few lines of example code? thx!

php -f /var/www/html/orm/bootstrap.php)

PHP Fatal error:  Uncaught Error: Class "Cake\Datasource\FactoryLocator" not found in /var/www/html/orm/bootstrap.php:21
Stack trace:
#0 {main}
  thrown in /var/www/html/orm/bootstrap.php on line 21

You want to have a look at the composer documentation again, and pay special attention to autoloading: Basic usage - Composer