Hi Awet,
Thank you for liking the KoolReport name. We hope after awhile you love what it brings as well :)
For your questions, the location of "koolreport" in your project is not important. You can put it at anywhere that you like. The most importance is you need to make reference to the "koolreport/core/autoload.php"
.
require_once "path/to/koolreport/core/autoload.php";
In our tutorial of How to use KoolReport in CodeIgniter we choose"libraries" because it is the way codeigniter organized 3rd party libraries and it is familiar with CodeIgniter's developers.
P.S: If you are using composer to install KoolReport, the library will be store in "vendor/koolreport" folder and you do not need to include koolreport/core/autoload.php. You only need to require_once "vendor/autoload.php";
because composer will load koolreport automatically.
Hope that helps.